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

devplacepy/routers/admin/users.py

@@ -9,6 +9,7 @@ from devplacepy.database import (
     get_table,
     build_pagination,
     get_post_counts_by_user_uids,
+    invalidate_admins_cache,
 )
 from devplacepy.utils import (
     require_admin,
@@ -133,6 +134,7 @@ async def admin_user_role(
     old_role = target_user.get("role") if target_user else None
     users.update({"uid": uid, "role": role}, ["uid"])
     clear_user_cache(uid)
+    invalidate_admins_cache()
     logger.info(f"Admin {admin['username']} set user {uid} role to {role}")
     audit.record(
         request,