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/services/devii/actions/catalog.py

@@ -853,6 +853,34 @@ ACTIONS: tuple[Action, ...] = (
         summary="Unfollow a user",
         params=(path("username", "Username to unfollow."),),
     ),
+    Action(
+        name="block_user",
+        method="POST",
+        path="/block/{username}",
+        summary="Block a user so their posts, comments and messages are hidden and they cannot notify you",
+        params=(path("username", "Username to block."),),
+    ),
+    Action(
+        name="unblock_user",
+        method="POST",
+        path="/block/unblock/{username}",
+        summary="Unblock a user",
+        params=(path("username", "Username to unblock."),),
+    ),
+    Action(
+        name="mute_user",
+        method="POST",
+        path="/mute/{username}",
+        summary="Mute a user so they can no longer create notifications for you",
+        params=(path("username", "Username to mute."),),
+    ),
+    Action(
+        name="unmute_user",
+        method="POST",
+        path="/mute/unmute/{username}",
+        summary="Unmute a user",
+        params=(path("username", "Username to unmute."),),
+    ),
     Action(
         name="list_followers",
         method="GET",