🔒 security: move IMAP credentials to request body and fix CI/pylint issues

- Moved IMAP credentials from query parameters to the request body for the test-connection endpoint.
- Created missing `__init__.py` files across `backend/app/` to fix CI `ModuleNotFoundError`.
- Reformatted `setup.py` and `user.py` using `black` to pass lint checks.
- Addressed Pylint warnings in `imap.py` (unused arguments, lazy logging, exception chaining).

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

backend/app/api/api_v1/endpoints/setup.py

@@ -1,4 +1,3 @@
-
 from fastapi import APIRouter, HTTPException, status
 from pydantic import BaseModel, EmailStr
 
@@ -38,7 +37,8 @@ class SystemConfigRequest(BaseModel):
 async def get_setup_status():
     """Get the current setup status"""
     return SetupStatusResponse(
-        is_setup_complete=setup_status["is_setup_complete"], app_name=setup_status["app_name"]
+        is_setup_complete=setup_status["is_setup_complete"],
+        app_name=setup_status["app_name"],
     )