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)

shared/browser/templates/oob_elements.html

@@ -0,0 +1,38 @@
+
+{% block oobs %}
+{% endblock %}
+
+<div
+  id="filter"
+  hx-swap-oob="outerHTML"
+>
+{% block filter %}
+{% endblock %}
+</div>
+
+
+
+<aside
+  id="aside"
+  hx-swap-oob="outerHTML"
+  class="hidden md:flex md:flex-col max-w-xs md:h-full md:min-h-0 mr-3"
+>
+{% block aside %}
+{% endblock %}
+</aside>
+
+<div id="root-menu" hx-swap-oob="outerHTML" class="md:hidden">
+  {% block mobile_menu %}
+  {% endblock %}
+</div>
+
+
+<section
+  id="main-panel"
+  class="flex-1 md:h-full md:min-h-0 overflow-y-auto overscroll-contain js-grid-viewport"
+>
+  {% block content %}
+
+  {% endblock %}
+
+</section>