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/templates/_bookmark_button.html

@@ -1,3 +1,3 @@
-<button type="button" class="post-action-btn bookmark-btn{% if _bookmarked %} bookmarked{% endif %}" data-bookmark-type="{{ _type }}" data-bookmark-uid="{{ _uid }}" title="{% if user %}Save{% else %}Log in to participate{% endif %}" aria-label="Save"{{ guest_disabled(user) }}>
+<button type="button" class="post-action-btn bookmark-btn{% if _bookmarked %} bookmarked{% endif %}" data-bookmark-type="{{ _type }}" data-bookmark-uid="{{ _uid }}" title="Save" aria-label="Save" aria-pressed="{% if _bookmarked %}true{% else %}false{% endif %}"{{ guest_disabled(user) }}>
     <span class="bookmark-icon">&#x1F516;</span> <span class="bookmark-label">{% if _bookmarked %}Saved{% else %}Save{% endif %}</span>
 </button>