docs: add block/mute user relations, emoji-sync CLI, and uid indexes

- Add `/block`, `/mute` endpoints with block/unblock and mute/unmute functionality in `routers/relations.py`, hiding blocked users' content everywhere except their own profile while muting only suppresses notifications
- Introduce `devplace emoji-sync` CLI command to regenerate `static/js/emoji-shortcodes.js` from the emoji library, documented in `CLAUDE.md` and wired in `cli.py`
- Create `get_blocked_uids()` database helper and apply it in `content.py` `load_detail()` to filter blocked users' posts from detail views
- Implement `_uid_index()` and `_drop_index()` helpers in `database.py` for unique uid indexes across tables, with `user_relations` added to `SOFT_DELETE_TABLES`
- Document new routes in `AGENTS.md` and `README.md`, including emoji shortcodes rendering behavior distinct from the emoji picker

tests/api/admin/aiusage/index.py

@@ -18,7 +18,7 @@ def _admin_aiusage(seeded_db):
 
 def test_admin_ai_usage_page_requires_admin(app_server):
     r = requests.get(f"{BASE_URL}/admin/ai-usage", allow_redirects=False)
-    assert r.status_code in (302, 401, 403)
+    assert r.status_code in (302, 303, 401, 403)
 
 
 def test_admin_ai_usage_page_returns_html(app_server, seeded_db):