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/docs_base.html

@@ -13,8 +13,8 @@
     "isAdmin": is_admin(user)
 } | tojson | safe }};</script>
 <div class="docs-layout">
-    <aside class="sidebar-card">
-        <div class="sidebar-heading">Documentation</div>
+    <aside class="sidebar-card" role="navigation" aria-label="Documentation">
+        <div class="sidebar-heading" role="heading" aria-level="2">Documentation</div>
         <form class="docs-search-form" method="get" action="/docs/search.html" role="search">
             <input type="search" name="q" value="{{ search_query|default('', true) }}" placeholder="Search docs…" aria-label="Search documentation" class="docs-search-input">
         </form>
@@ -24,9 +24,9 @@
                 Search
             </a>
             {% for audience, tiers in nav %}
-            <div class="sidebar-heading sidebar-tier">{{ audience }}</div>
+            <div class="sidebar-heading sidebar-tier" role="heading" aria-level="2">{{ audience }}</div>
             {% for section, section_pages in tiers %}
-            <div class="sidebar-heading sidebar-subheading">{{ section }}</div>
+            <div class="sidebar-heading sidebar-subheading" role="heading" aria-level="3">{{ section }}</div>
             {% for p in section_pages %}
             <a href="/docs/{{ p.slug }}.html" class="sidebar-link sidebar-link-nested {% if p.slug == current %}active{% endif %}">
                 <span class="icon">&#x1F4D8;</span>
@@ -36,7 +36,7 @@
             {% endfor %}
             {% endfor %}
         </div>
-        <div class="sidebar-heading docs-download-heading">Download</div>
+        <div class="sidebar-heading docs-download-heading" role="heading" aria-level="2">Download</div>
         <div class="sidebar-nav">
             <a href="/docs/download.html" class="sidebar-link"><span class="icon">&#x1F4E5;</span> Single HTML</a>
             <a href="/docs/download.md" class="sidebar-link"><span class="icon">&#x1F4DD;</span> Markdown</a>