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/css/game.css

@@ -501,3 +501,27 @@
 .game-perks {
     margin-top: var(--space-xl);
 }
+
+.game-legacy {
+    margin-top: var(--space-xl);
+}
+
+.game-legacy-note {
+    color: var(--text-muted);
+    font-size: 0.85rem;
+    margin: 0 0 var(--space-md);
+}
+
+.legacy-card {
+    border-color: #f5c518;
+}
+
+.game-plot-golden {
+    border-color: #f5c518;
+    box-shadow: 0 0 0 1px #f5c518 inset, 0 0 12px rgba(245, 197, 24, 0.4);
+}
+
+.plot-steal-locked {
+    color: var(--warning);
+    font-family: var(--font-mono);
+}

devplacepy/static/css/profile.css

@@ -28,6 +28,11 @@
     margin: 0 auto;
 }
 
+.avatar-regen-btn {
+    display: block;
+    margin: 0.5rem auto 0;
+}
+
 .profile-name {
     font-size: 1.25rem;
     font-weight: 700;