feat(app): add plugin system with auth plugin and static assets

Add new application structure:
- app/main.py - application entry point
- app/plugins/ - plugin system with auth plugin:
  - api/ - REST API endpoints and schemas
  - authorization/ - auth policies, providers, hooks
  - domain/ - business logic (service, models, jwt, password)
  - injection/ - route injection and guards
  - ops/ - operational utilities
  - runtime/ - runtime configuration
  - security/ - middleware, CSRF, dependencies
  - storage/ - user repositories and models
- app/static/ - static assets (scalar.js for API docs)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/plugins/auth/authorization/authentication.py

@@ -0,0 +1,43 @@
+"""Authentication helpers used by auth-plugin authorization decorators."""
+
+from __future__ import annotations
+
+from fastapi import Request
+
+from app.plugins.auth.authorization.providers import PermissionProvider, default_permission_provider
+from app.plugins.auth.authorization.types import AuthContext
+
+
+def get_auth_context(request: Request) -> AuthContext | None:
+    """Get AuthContext, preferring Starlette-style request.auth."""
+
+    auth = request.scope.get("auth")
+    if isinstance(auth, AuthContext):
+        return auth
+    return getattr(request.state, "auth", None)
+
+
+def set_auth_context(request: Request, auth_context: AuthContext) -> AuthContext:
+    """Persist AuthContext on the standard request surfaces."""
+
+    request.scope["auth"] = auth_context
+    request.state.auth = auth_context
+    return auth_context
+
+
+async def authenticate_request(
+    request: Request,
+    *,
+    permission_provider: PermissionProvider = default_permission_provider,
+) -> AuthContext:
+    """Authenticate request and build AuthContext."""
+
+    from app.plugins.auth.security.dependencies import get_optional_user_from_request
+
+    user = await get_optional_user_from_request(request)
+    if user is None:
+        return AuthContext(user=None, permissions=[])
+    return AuthContext(user=user, permissions=permission_provider(user))
+
+
+__all__ = ["authenticate_request", "get_auth_context", "set_auth_context"]