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/providers.py

@@ -0,0 +1,18 @@
+"""Default permission provider hooks for auth-plugin authorization."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+
+from app.plugins.auth.authorization.types import ALL_PERMISSIONS
+
+PermissionProvider = Callable[[object], list[str]]
+
+
+def default_permission_provider(user: object) -> list[str]:
+    """Return the current static permission set for an authenticated user."""
+
+    return list(ALL_PERMISSIONS)
+
+
+__all__ = ["PermissionProvider", "default_permission_provider"]