fix: sync user name from external auth API and fix audit log schema

- Auth router: Extract user name from nested data.userInfo.name structure
- Auth router: Sync user name on every login (not just on user creation)
- Audit schema: Change changes field type to Optional[Any] to support
  both list and dict formats (fixes 500 error on audit page)

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

backend/app/schemas/audit.py

@@ -10,7 +10,7 @@ class AuditLogResponse(BaseModel):
     resource_id: Optional[str]
     user_id: Optional[str]
     action: str
-    changes: Optional[List[dict]]
+    changes: Optional[Any]  # Can be List[dict] or dict depending on event type
     request_metadata: Optional[dict]
     sensitivity_level: str
     checksum: str