fix: improve SMTP configuration and error handling

- Change default use_tls from True to False to match typical STARTTLS setup
- Add MailDeliveryError exception for mail delivery failures
- Wrap send_mail calls in try-catch blocks to handle errors gracefully
- Return 502 status code with error details when mail delivery fails
- Add SMTP security mode selector in frontend (STARTTLS/TLS/None)
- Add test mail form to admin panel
- Handle empty SMTP credentials properly in update_mail_settings
- Catch

backend/app/api/routes/admin.py

@@ -17,6 +17,7 @@ from app.schemas.common import (
 )
 from app.services.audit import audit
 from app.services.mail import (
+    MailDeliveryError,
     get_mail_settings,
     send_mail,
     serialize_mail_settings,
@@ -49,7 +50,10 @@ def create_user(payload: UserCreate, admin: User = Depends(current_admin), db: S
     db.add(user)
     db.flush()
     if payload.send_invite:
-        send_invitation(db, user)
+        try:
+            send_invitation(db, user)
+        except MailDeliveryError as exc:
+            raise HTTPException(status_code=502, detail=str(exc)) from exc
     audit(db, admin, "admin.user.create", "user", user.id)
     db.commit()
     db.refresh(user)
@@ -86,7 +90,10 @@ def reset_password(user_id: str, admin: User = Depends(current_admin), db: Sessi
     if not user:
         raise HTTPException(status_code=404, detail="User not found")
     token = create_reset_token(db, user)
-    send_mail(db, user.email, "NexaPantry password reset", f"Reset token: {token}")
+    try:
+        send_mail(db, user.email, "NexaPantry password reset", f"Reset token: {token}")
+    except MailDeliveryError as exc:
+        raise HTTPException(status_code=502, detail=str(exc)) from exc
     audit(db, admin, "admin.user.reset_password", "user", user.id)
     db.commit()
     return Message(message="Password reset mail sent")
@@ -112,7 +119,10 @@ def save_mail_settings(payload: MailSettingsIn, admin: User = Depends(current_ad
 
 @router.post("/mail/test", response_model=Message)
 def test_mail(payload: TestMailIn, db: Session = Depends(get_db)) -> Message:
-    send_mail(db, str(payload.to), "NexaPantry test mail", "SMTP is configured correctly.")
+    try:
+        send_mail(db, str(payload.to), "NexaPantry test mail", "SMTP is configured correctly.")
+    except MailDeliveryError as exc:
+        raise HTTPException(status_code=502, detail=str(exc)) from exc
     return Message(message="Test mail sent")