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)

events/bp/calendar_entry/admin/routes.py

@@ -0,0 +1,28 @@
+from __future__ import annotations
+
+from quart import (
+    render_template, make_response, Blueprint
+)
+
+
+from shared.browser.app.authz import require_admin
+
+
+def register():
+    bp = Blueprint("admin", __name__, url_prefix='/admin')
+    
+    # ---------- Pages ----------
+    @bp.get("/")
+    @require_admin
+    async def admin(entry_id: int, **kwargs):
+        from shared.browser.app.utils.htmx import is_htmx_request
+
+        # Determine which template to use based on request type
+        if not is_htmx_request():
+            # Normal browser request: full page with layout
+            html = await render_template("_types/entry/admin/index.html")
+        else:
+            html = await render_template("_types/entry/admin/_oob_elements.html")
+
+        return await make_response(html)
+    return bp