feat: add per-user avatar seed regeneration with irreversible random avatar replacement

Implement a new `avatar_seed` column on the users table that overrides the username-based seed for Multiavatar generation. Introduce a null-safe `avatar_seed(user)` choke point in `avatar.py` that resolves `user.get("avatar_seed") or user.get("username")`, registered as a Jinja global so every render site (`_avatar_link.html`, `avatar_url(...)` calls, SEO `og_image`, issues ad-hoc dicts, devRant payload/PNG) propagates a regenerated seed. Add `POST /profile/{username}/regenerate-avatar` endpoint (owner-or-admin only) that writes a fresh `generate_uid()` to `avatar_seed`, invalidates the target's user cache, and audits `profile.avatar.regenerate`. The previous seed is overwritten and never stored, making regeneration irreversible. Document the feature in `AGENTS.md` and `README.md`, add the API endpoint to `docs_api.py`, and include the `regenerate_avatar` Devii tool in `CONFIRM_REQUIRED`.

devplacepy/routers/profile/__init__.py

@@ -5,6 +5,7 @@ from fastapi import APIRouter
 from devplacepy.routers.profile import (
     ai_correction,
     ai_modifier,
+    avatar,
     customization,
     index,
     notifications,
@@ -18,6 +19,7 @@ router.include_router(customization.router)
 router.include_router(notifications.router)
 router.include_router(ai_correction.router)
 router.include_router(ai_modifier.router)
+router.include_router(avatar.router)
 router.include_router(telegram.router)
 
 __all__ = ["router", "_ai_quota"]