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/__init__.py

@@ -0,0 +1,31 @@
+"""Authorization layer for the auth plugin."""
+
+from app.plugins.auth.authorization.authentication import get_auth_context
+from app.plugins.auth.authorization.hooks import (
+    AuthzHooks,
+    build_authz_hooks,
+    build_permission_provider,
+    build_policy_chain_builder,
+    get_authz_hooks,
+    get_default_authz_hooks,
+)
+from app.plugins.auth.authorization.types import (
+    AuthContext,
+    Permissions,
+    ALL_PERMISSIONS,
+)
+
+_ALL_PERMISSIONS = ALL_PERMISSIONS
+
+__all__ = [
+    "AuthContext",
+    "AuthzHooks",
+    "Permissions",
+    "_ALL_PERMISSIONS",
+    "build_authz_hooks",
+    "build_permission_provider",
+    "build_policy_chain_builder",
+    "get_auth_context",
+    "get_authz_hooks",
+    "get_default_authz_hooks",
+]