Refactor auth and setup services

- Updated auth_service.py to improve authentication logic
- Modified setup_service.py for better configuration handling
- Added comprehensive tests for setup_service
- Updated documentation in Tasks.md

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/tests/test_services/test_setup_service.py

@@ -12,7 +12,7 @@ import pytest
 
 from app.db import init_db
 from app.repositories import settings_repo
-from app.services import settings_service, setup_service
+from app.services import auth_service, settings_service, setup_service
 
 
 @pytest.fixture
@@ -113,7 +113,7 @@ class TestRunSetup:
             timezone="UTC",
             session_duration_minutes=60,
         )
-        stored = await setup_service.get_password_hash(db)
+        stored = await auth_service.get_password_hash(db)
         assert stored is not None
         assert stored != "mypassword1"
         # Verify it is a valid bcrypt hash.