🧹 [code health improvement] Silence unused imports in models/__init__.py

Updated `backend/app/models/__init__.py` to use explicit re-exports (e.g., `from app.models.database_models import User as User`) to satisfy static analysis tools and improve code health. This follows PEP 484 and silences "unused import" warnings while maintaining the public API for the models package.

🎯 **What:** The code health issue addressed is unused imports in `models/__init__.py` being flagged by static analysis tools.
💡 **Why:** This improves maintainability and silences noise in linting reports without breaking the package's public API.
✅ **Verification:** Confirmed via code review and manual inspection that models are still correctly exported and correctly used in other parts of the codebase.
✨ **Result:** The codebase is now cleaner and follows Python best practices for package exports.

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

backend/app/models/__init__.py

@@ -1,18 +1,18 @@
 """Models package"""
 
 from app.models.database_models import (
-    User,
-    MailAccount,
-    ProcessingRun,
-    ProcessingLog,
-    NotificationConfig,
-    MailServerPreset,
-    SubscriptionPlan,
-    AuditLog,
-    SubscriptionTier,
-    MailProtocol,
-    AccountStatus,
-    NotificationChannel,
+    AccountStatus as AccountStatus,
+    AuditLog as AuditLog,
+    MailAccount as MailAccount,
+    MailProtocol as MailProtocol,
+    MailServerPreset as MailServerPreset,
+    NotificationChannel as NotificationChannel,
+    NotificationConfig as NotificationConfig,
+    ProcessingLog as ProcessingLog,
+    ProcessingRun as ProcessingRun,
+    SubscriptionPlan as SubscriptionPlan,
+    SubscriptionTier as SubscriptionTier,
+    User as User,
 )
 
 __all__ = [