Add thread notifications, SEO topic pages, and fix quiz auto-advance

Notifications: a new "thread" type notifies every other commenter on a
post whenever anyone comments on it, disregarding reply hierarchy -
excluding the actor and whoever already got a comment/reply
notification for that same event, so no one is double-notified.
Implemented via a background-deferred fan-out mirroring the existing
mention-notification pattern.

SEO: discussion_forum_posting() now embeds up to 20 of a post's
comments as nested schema.org Comment entities (not just an aggregate
count), and a new /topics hub plus /topics/{topic} pages give the
feed's topic filter real, independently crawlable/indexable URLs -
/feed?topic=X was never indexable since its canonical strips the
query string back to bare /feed. Both are wired end to end (schemas,
Devii actions, docs API, sitemap, locustfile load-test coverage).

Quiz player: the auto-advance to the next question used to hide the
just-answered slide in the same tick as rendering the grade, so on
any multi-question quiz the Correct/Not correct feedback was never
actually visible before the view moved on. Delayed via setTimeout,
with the pending timer cleared on manual navigation and on
disconnect so it can't race or fire on a removed component.

Also includes other local changes already in progress in this
working tree before this session (messaging, push delivery,
deepsearch jobs, game economy, quiz builder) - verified by the full
suite passing (3467 tests) but not authored or individually reviewed
in this session.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VL9Xn57W5UR3HZbbuuzxdK

CLAUDE.md

@@ -19,7 +19,7 @@ DevPlace is a server-rendered social network for developers. FastAPI backend ser
 ## Commands
 
 ```bash
-make install        # pip install -e . + playwright install chromium
+make install        # create .venv if needed, pip install -e ".[dev]", playwright chromium
 make ppy            # build the single shared container image (ppy:latest); run once before launching instances
 make dev            # uvicorn --reload on port 10500, backlog 4096
 make prod           # uvicorn --workers $(WEB_WORKERS) (defaults to nproc), port 10500 (backlog 8192)
@@ -33,6 +33,8 @@ make locust         # Locust load test, interactive web UI
 make locust-headless  # Locust CLI mode for CI
 ```
 
+Every Python make target (`install`, `dev`, `prod`, `test*`, `coverage*`, `locust*`) uses `.venv/bin/python`. If `.venv` is missing, make creates it from `python3`, installs `-e ".[dev]"`, and installs Playwright Chromium before running the target. `make install` refreshes that environment. `make clean` removes `.venv` as well as stray bytecode.
+
 The Makefile exports `PYTHONDONTWRITEBYTECODE=1` for every recipe, so no `.pyc` files or `__pycache__` directories are written by any `make` target. Keep it that way - do not add a target that re-enables bytecode writing. `make clean` removes any stray bytecode left from running Python outside make.
 
 Preliminary validation: confirm `python -c "from devplacepy.main import app"` imports clean and check each touched language manually (Python compiles/imports, JS parses, CSS braces and HTML tags balance). These checks are gates on the way to the real validation, never a substitute for it: **every change ends with the full test suite (`make test` - all three tiers, every test) and it must pass.**
@@ -183,6 +185,7 @@ Routers in `devplacepy/routers/` are organised as a **directory tree that mirror
 |--------|--------|
 | `/auth` | auth/ package |
 | `/feed`, `/posts`, `/comments` | flat files |
+| `/topics` | topics.py - crawlable per-topic category index pages (`/topics` hub, `/topics/{topic}` listing) |
 | `/projects`, `/projects/{slug}/files`, `/projects/{slug}/containers` | projects/ package - see `routers/projects/CLAUDE.md` |
 | `/profile` | profile/ package (customization, notifications, ai-correction, ai-modifier, interactions, telegram, usage) |
 | `/messages` | messages.py - see `services/messaging/CLAUDE.md` |
@@ -282,7 +285,7 @@ The escape hatch is deliberately two-factor and must never be self-served: after
 
 - **No comments, no docstrings in source.** Code is self-documenting.
 - **Forbidden variable name patterns:** `_new`, `_old`, `_temp`, `_v2`, `better_`, `my_`, `the_`.
-- **Outbound HTTP goes through the stealth client only.** Never instantiate a bare `httpx.AsyncClient(...)`/`httpx.Client(...)` for outbound traffic - build it via `devplacepy.stealth.stealth_async_client(...)`/`stealth_sync_client(...)`. The async factory routes bytes through **`curl_cffi` (curl-impersonate, BoringSSL)** behind an `httpx` transport adapter, so TLS JA3/JA4 and the HTTP/2 fingerprint match Chrome 146 byte-for-byte; falls back to a pure-httpx Chrome-aligned transport if `curl_cffi` is missing. Applies to news, gateway upstream, Devii/DeepSearch/SEO fetch, gitea, push, attachments. SSRF-guarded fetches via `net_guard.guarded_async_client(...)` get the fingerprint automatically. Sole exception: the reverse-proxy forwarding core `services/containers/forward.py` (and the three routers that call it - `routers/proxy.py`, `routers/tunnel.py`, the workspace editor route), which relays the user's own headers verbatim and therefore keeps a plain `httpx.AsyncClient`; bolting the Chrome identity onto it would overwrite the very headers it exists to forward. **Load-bearing gotcha:** cleartext `http://` is forced to HTTP/1.1 (`curl_transport.http_version_for`) - the Chrome-impersonation profile defaults to HTTP/2, but a plaintext origin has no TLS/ALPN to negotiate h2 and uvicorn (HTTP/1.1 only) returns `400 "Invalid HTTP request received."` once a cleartext HTTP/2 body crosses ~128KB. Every internal AI consumer calls `INTERNAL_GATEWAY_URL` = `http://localhost:<port>/openai/v1/...`, so without this override a large Devii turn (big system prompt + tool list) fails on every request. `https://` keeps the HTTP/2 default. `stealth_sync_client` stays pure-httpx Chrome-aligned (no curl_cffi sync adapter). **Never bolt a hand-written browser-header dict (UA/`sec-ch-ua`/`Sec-Fetch-*`) onto a `stealth_async_client`/`stealth_sync_client` call** - curl_cffi's impersonation already emits an internally-consistent Chrome 146 identity across TLS, UA, and Client Hints; a caller-supplied header set claiming a different Chrome version or platform creates a UA-vs-TLS-vs-Client-Hints mismatch that is a textbook anti-bot tripwire (this was a real bug in Devii's `fetch_url`/`http_request` tool, fixed by deleting its hardcoded Chrome-131 header block). `stealth.detect_consent_gate(html)` recognizes the common JS-redirect cookie-consent wall pattern (DPG Media's `nu.nl` and sibling sites, and generically any page gated behind a `decodeURIComponent(...)` callback referencing a "privacy gate"/`consent.js`) - reuse it wherever a fetched page's real content sits behind that gate rather than special-casing a domain. `stealth_transport`/`stealth_async_client`/`stealth_sync_client` all accept a `proxy=` override, defaulting to `stealth.configured_proxy_url()` (the admin-editable `outbound_proxy_url` site setting, falling back to `DEVPLACE_OUTBOUND_PROXY_URL` when the setting is unset) - this is the only real fix for a destination that blocks by IP/ASN reputation (e.g. reddit.com returns an identical "blocked by network security" page across every TLS/header fingerprint tried, confirmed by testing curl_cffi's full impersonation list - it is blocking the datacenter ASN outright, not fingerprinting the client).
+- **Outbound HTTP goes through the stealth client only.** Never instantiate a bare `httpx.AsyncClient(...)`/`httpx.Client(...)` for outbound traffic - build it via `devplacepy.stealth.stealth_async_client(...)`/`stealth_sync_client(...)`. The async factory routes bytes through **`curl_cffi` (curl-impersonate, BoringSSL)** behind an `httpx` transport adapter, so TLS JA3/JA4 and the HTTP/2 fingerprint match Chrome 146 byte-for-byte; falls back to a pure-httpx Chrome-aligned transport if `curl_cffi` is missing. Applies to news, gateway upstream, Devii/DeepSearch/SEO fetch, gitea, web push, attachments. SSRF-guarded fetches via `net_guard.guarded_async_client(...)` get the fingerprint automatically. Two exceptions keep a plain `httpx.AsyncClient`: (1) the reverse-proxy forwarding core `services/containers/forward.py` (and the three routers that call it - `routers/proxy.py`, `routers/tunnel.py`, the workspace editor route), which relays the user's own headers verbatim - bolting the Chrome identity onto it would overwrite the very headers it exists to forward; (2) the APNs provider (`push/providers/apns.py` `gateway_client` / `delivery_client`) which talks to Apple's HTTP/2 provider API with `httpx.AsyncClient(http2=True, trust_env=False)` - Chrome impersonation, HTTP/2 PRIORITY frames, HPACK indexing of `:path`/`authorization`, extra browser headers, and the outbound proxy all break or starve that API. Web Push stays on stealth. **Load-bearing gotcha:** cleartext `http://` is forced to HTTP/1.1 (`curl_transport.http_version_for`) - the Chrome-impersonation profile defaults to HTTP/2, but a plaintext origin has no TLS/ALPN to negotiate h2 and uvicorn (HTTP/1.1 only) returns `400 "Invalid HTTP request received."` once a cleartext HTTP/2 body crosses ~128KB. Every internal AI consumer calls `INTERNAL_GATEWAY_URL` = `http://localhost:<port>/openai/v1/...`, so without this override a large Devii turn (big system prompt + tool list) fails on every request. `https://` keeps the HTTP/2 default. `stealth_sync_client` stays pure-httpx Chrome-aligned (no curl_cffi sync adapter). **Never bolt a hand-written browser-header dict (UA/`sec-ch-ua`/`Sec-Fetch-*`) onto a `stealth_async_client`/`stealth_sync_client` call** - curl_cffi's impersonation already emits an internally-consistent Chrome 146 identity across TLS, UA, and Client Hints; a caller-supplied header set claiming a different Chrome version or platform creates a UA-vs-TLS-vs-Client-Hints mismatch that is a textbook anti-bot tripwire (this was a real bug in Devii's `fetch_url`/`http_request` tool, fixed by deleting its hardcoded Chrome-131 header block). `stealth.detect_consent_gate(html)` recognizes the common JS-redirect cookie-consent wall pattern (DPG Media's `nu.nl` and sibling sites, and generically any page gated behind a `decodeURIComponent(...)` callback referencing a "privacy gate"/`consent.js`) - reuse it wherever a fetched page's real content sits behind that gate rather than special-casing a domain. `stealth_transport`/`stealth_async_client`/`stealth_sync_client` all accept a `proxy=` override, defaulting to `stealth.configured_proxy_url()` (the admin-editable `outbound_proxy_url` site setting, falling back to `DEVPLACE_OUTBOUND_PROXY_URL` when the setting is unset) - this is the only real fix for a destination that blocks by IP/ASN reputation (e.g. reddit.com returns an identical "blocked by network security" page across every TLS/header fingerprint tried, confirmed by testing curl_cffi's full impersonation list - it is blocking the datacenter ASN outright, not fingerprinting the client).
 - **Form validation is Pydantic-native.** Routers declare `data: Annotated[SomeForm, Form()]` (models in `models.py`); the global `RequestValidationError` handler re-renders auth pages with messages (400) or redirects other routes. Read raw `await request.form()` only when also reading an uploaded file alongside a model.
 - **`RedirectResponse(url=..., status_code=302)`** - always pass `status_code` as an integer literal, never `status.HTTP_302_FOUND`.
 - **Ownership checks:** compare `resource["user_uid"] == user["uid"]` before edit/delete (use `content.is_owner`). **Deletes additionally allow any admin:** `is_owner(...) or is_admin(user)` on every content delete endpoint, so an administrator may delete any member's content while members are limited to their own. Edits stay owner-only. Deletes are **soft** and cascade under one shared stamp - see `devplacepy/database/CLAUDE.md`.