feat: add load_traffic_file tool for importing HAR and flow files

[sleeyax]

Import flows from HAR or mitmproxy flow files into the traffic DB without running the proxy. Supports scope filtering and append mode.

Example usage using GitHub copilot in vscode:

[snapspecter]

Thanks, this is definitely a useful feature.

I made a few small changes before merging:

Async Unblocking: Wrapped the import_from_file execution in asyncio.to_thread so that reading large HAR/flow files won't block the MCP server's main event loop.
Security / Path Validation: Added os.path.exists validation and restricted imports to files ending in .har, .mitm, or .flow to prevent any unintended arbitrary file reads via the MCP interface.
Scope Checking: Fixed a minor issue where scope checking was using a basic substring match instead of checking for exact domain/suffix matches (apple.com previously would have incorrectly matched myapple.com).

[sleeyax]

Perfect, thank you for improving and merging!