feat: JWT auth, user management, audit logging system

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

backend/app/schemas/user.py

@@ -0,0 +1,19 @@
+from pydantic import BaseModel, ConfigDict
+from datetime import datetime
+
+
+class UserResponse(BaseModel):
+    id: str
+    username: str
+    email: str
+    role: str
+    is_active: bool
+    is_approved: bool
+    created_at: datetime
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+class UserUpdateRequest(BaseModel):
+    role: str | None = None
+    is_active: bool | None = None