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/macros/glyphs.html

@@ -0,0 +1,17 @@
+{% macro opener(group=False) %}
+    <svg
+        class="h-4 w-4 transition-transform group-open{{ '/' + group if group else ''}}:rotate-180"
+        xmlns="http://www.w3.org/2000/svg"
+        viewBox="0 0 24 24"
+        fill="none"
+        stroke="currentColor"
+      >
+        <path
+          stroke-linecap="round"
+          stroke-linejoin="round"
+          stroke-width="2"
+          d="M6 9l6 6 6-6"
+        />
+      </svg>
+
+{% endmacro %}