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/static/js/Application.js

@@ -18,6 +18,7 @@ import { ReactionBar } from "./ReactionBar.js";
 import { BookmarkManager } from "./BookmarkManager.js";
 import { PollManager } from "./PollManager.js";
 import { ApiKeyManager } from "./ApiKeyManager.js";
+import { AvatarRegenerator } from "./AvatarRegenerator.js";
 import { CustomizationToggle } from "./CustomizationToggle.js";
 import { NotificationPrefs } from "./NotificationPrefs.js";
 import { AiCorrection } from "./AiCorrection.js";
@@ -67,6 +68,7 @@ class Application {
         this.bookmarks = new BookmarkManager();
         this.polls = new PollManager();
         this.apiKey = new ApiKeyManager();
+        this.avatarRegenerator = new AvatarRegenerator();
         this.customizationToggle = new CustomizationToggle();
         this.notificationPrefs = new NotificationPrefs(this.pubsub);
         this.aiCorrection = new AiCorrection();