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/_poll.html

@@ -7,7 +7,7 @@
             <span class="poll-option-bar" style="width: {{ opt.pct }}%;"></span>
             <span class="poll-option-label">{{ render_title(opt.label) }}</span>
             <span class="poll-option-meta">
-                <span class="poll-option-check"{% if _poll.my_choice != opt.uid %} hidden{% endif %}>&#x2713;</span>
+                <span class="poll-option-check" aria-hidden="true"{% if _poll.my_choice != opt.uid %} hidden{% endif %}>&#x2713;</span>
                 <span class="poll-option-pct">{{ opt.pct }}%</span>
             </span>
         </button>