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)

cart/bp/fragments/__init__.py

@@ -0,0 +1 @@
+from .routes import register as register_fragments

cart/bp/fragments/routes.py

@@ -0,0 +1,70 @@
+"""Cart app fragment endpoints.
+
+Exposes HTML fragments at ``/internal/fragments/<type>`` for consumption
+by other coop apps via the fragment client.
+
+Fragments:
+  cart-mini          Cart icon with badge (or logo when empty)
+  account-nav-item   "orders" link for account dashboard
+"""
+
+from __future__ import annotations
+
+from quart import Blueprint, Response, request, render_template, g
+
+from shared.infrastructure.fragments import FRAGMENT_HEADER
+
+
+def register():
+    bp = Blueprint("fragments", __name__, url_prefix="/internal/fragments")
+
+    # ---------------------------------------------------------------
+    # Fragment handlers
+    # ---------------------------------------------------------------
+
+    async def _cart_mini():
+        from shared.services.registry import services
+
+        user_id = request.args.get("user_id", type=int)
+        session_id = request.args.get("session_id")
+
+        summary = await services.cart.cart_summary(
+            g.s, user_id=user_id, session_id=session_id,
+        )
+        count = summary.count + summary.calendar_count + summary.ticket_count
+        return await render_template("fragments/cart_mini.html", cart_count=count)
+
+    async def _account_nav_item():
+        from shared.infrastructure.urls import cart_url
+
+        href = cart_url("/orders/")
+        return (
+            '<div class="relative nav-group">'
+            f'<a href="{href}" class="justify-center cursor-pointer flex flex-row '
+            'items-center gap-2 rounded bg-stone-200 text-black p-3" data-hx-disable>'
+            'orders</a></div>'
+        )
+
+    _handlers = {
+        "cart-mini": _cart_mini,
+        "account-nav-item": _account_nav_item,
+    }
+
+    # ---------------------------------------------------------------
+    # Routing
+    # ---------------------------------------------------------------
+
+    @bp.before_request
+    async def _require_fragment_header():
+        if not request.headers.get(FRAGMENT_HEADER):
+            return Response("", status=403)
+
+    @bp.get("/<fragment_type>")
+    async def get_fragment(fragment_type: str):
+        handler = _handlers.get(fragment_type)
+        if handler is None:
+            return Response("", status=200, content_type="text/html")
+        html = await handler()
+        return Response(html, status=200, content_type="text/html")
+
+    return bp