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/timeline.html

@@ -0,0 +1,19 @@
+{% extends "_types/social/index.html" %}
+
+{% block title %}{{ "Home" if timeline_type == "home" else "Public" }} Timeline — Rose Ash{% endblock %}
+
+{% block social_content %}
+<div class="flex items-center justify-between mb-6">
+  <h1 class="text-2xl font-bold">{{ "Home" if timeline_type == "home" else "Public" }} Timeline</h1>
+  {% if actor %}
+    <a href="{{ url_for('social.compose_form') }}"
+       class="bg-stone-800 text-white px-4 py-2 rounded hover:bg-stone-700">
+      Compose
+    </a>
+  {% endif %}
+</div>
+
+<div id="timeline">
+  {% include "federation/_timeline_items.html" %}
+</div>
+{% endblock %}