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/bp/auth/services/__init__.py

@@ -0,0 +1,24 @@
+from .login_redirect import pop_login_redirect_target, store_login_redirect_target
+from .auth_operations import (
+    get_app_host,
+    get_app_root,
+    send_magic_email,
+    load_user_by_id,
+    find_or_create_user,
+    create_magic_link,
+    validate_magic_link,
+    validate_email,
+)
+
+__all__ = [
+    "pop_login_redirect_target",
+    "store_login_redirect_target",
+    "get_app_host",
+    "get_app_root",
+    "send_magic_email",
+    "load_user_by_id",
+    "find_or_create_user",
+    "create_magic_link",
+    "validate_magic_link",
+    "validate_email",
+]