Potential fix for code scanning alert no. 12: Information exposure through an exception

[GitTimeraider]

Potential fix for https://github.com/GitTimeraider/Directadmin-Emailforwarder/security/code-scanning/12

To fix the problem, we should avoid returning the raw exception message to the client. Instead, we should log the exception (including the stack trace) on the server for debugging, and return a generic error message to the client. This ensures that sensitive information is not leaked, while still allowing developers to diagnose issues using server logs.

Steps:

• In the except block of the test_connection route, replace str(e) in the JSON response with a generic error message (e.g., "An internal error has occurred.").
• Log the exception and stack trace to the server console using print() or a logging framework.
• No changes to imports are needed, as traceback is already imported.

Files/regions to change:

• Only app/settings.py, lines 120-122 (the except block in test_connection).

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