fix: propagate SMTP exceptions in diagnostic endpoint to display exact SMTP error details

backend/app/api/endpoints.py

@@ -361,7 +361,7 @@ async def test_email(email: str = None):
         
     try:
         # Run synchronous send directly to capture the exact exception stack trace
-        result = send_verification_email(to_email, "123456")
+        result = send_verification_email(to_email, "123456", raise_on_error=True)
         if result:
             return {
                 "success": True,

backend/app/services/email_service.py

@@ -111,7 +111,7 @@ def send_price_alert_email(to_email: str, ticker: str, condition: str, target_pr
         return False
 
 
-def send_verification_email(to_email: str, code: str) -> bool:
+def send_verification_email(to_email: str, code: str, raise_on_error: bool = False) -> bool:
     """
     Sends a registration verification OTP email using SMTP config, or logs to console as a fallback.
     """
@@ -196,4 +196,6 @@ def send_verification_email(to_email: str, code: str) -> bool:
         return True
     except Exception as e:
         logger.error(f"Failed to send verification email via SMTP host {settings.SMTP_HOST}: {e}")
+        if raise_on_error:
+            raise e
         return False