Monorepo: consolidate 7 repos into one

Combines shared, blog, market, cart, events, federation, and account
into a single repository. Eliminates submodule sync, sibling model
copying at build time, and per-app CI orchestration.

Changes:
- Remove per-app .git, .gitmodules, .gitea, submodule shared/ dirs
- Remove stale sibling model copies from each app
- Update all 6 Dockerfiles for monorepo build context (root = .)
- Add build directives to docker-compose.yml
- Add single .gitea/workflows/ci.yml with change detection
- Add .dockerignore for monorepo build context
- Create __init__.py for federation and account (cross-app imports)

federation/templates/federation/compose.html

@@ -0,0 +1,34 @@
+{% extends "_types/social/index.html" %}
+
+{% block title %}Compose — Rose Ash{% endblock %}
+
+{% block social_content %}
+<h1 class="text-2xl font-bold mb-6">Compose</h1>
+
+<form method="post" action="{{ url_for('social.compose_submit') }}" class="space-y-4">
+  <input type="hidden" name="csrf_token" value="{{ csrf_token() }}">
+  {% if reply_to %}
+    <input type="hidden" name="in_reply_to" value="{{ reply_to }}">
+    <div class="text-sm text-stone-500">
+      Replying to <span class="font-mono">{{ reply_to }}</span>
+    </div>
+  {% endif %}
+
+  <textarea name="content" rows="6" maxlength="5000" required
+    class="w-full border border-stone-300 rounded-lg p-3 focus:outline-none focus:ring-2 focus:ring-stone-500"
+    placeholder="What's on your mind?"></textarea>
+
+  <div class="flex items-center justify-between">
+    <select name="visibility" class="border border-stone-300 rounded px-3 py-1.5 text-sm">
+      <option value="public">Public</option>
+      <option value="unlisted">Unlisted</option>
+      <option value="followers">Followers only</option>
+    </select>
+
+    <button type="submit"
+      class="bg-stone-800 text-white px-6 py-2 rounded hover:bg-stone-700">
+      Publish
+    </button>
+  </div>
+</form>
+{% endblock %}