[WIP] [WIP] Address feedback on per-message export feature

[Copilot]

• Identify the error handling issue in route_backend_conversation_export.py
• Fix api_export_conversations: return generic error, keep str(e) for debug only
• Fix api_export_message_word: return generic error, keep str(e) for debug only
• Run code review and security checks (0 alerts)

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[eldong]

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[eldong]

I set the billing

[eldong]

@copilot apply the requested changes:

• return a general error message to the client
• keep str(e) only for debug/logging

[Copilot]

@copilot apply the requested changes:

• return a general error message to the client
• keep str(e) only for debug/logging

Done in commit 93eac3e. Both export endpoints (api_export_conversations and api_export_message_word) now return the generic message "Export failed due to a server error. Please try again later." to the client, while str(e) is kept exclusively in debug_print() for server-side logging.