Add timeout parameter to download_video HTTP requests in video_describer.py

[chigwell]

User Story
As a software maintainer,
I want to add a timeout parameter to the download_video method's HTTP requests
so that the application avoids indefinite hangs when servers are unresponsive.

Background
The current download_video method in frame_story/video_describer.py uses requests.get(video_url) without a timeout. This creates reliability risks:

• Unresponsive servers or unstable connections could freeze the process indefinitely.
• No error recovery mechanism exists for stalled downloads, impacting user experience.
  The method is critical for fetching remote videos (e.g., get_video_descriptions uses it to retrieve URLs like http://example.com/video.mp4).

Acceptance Criteria

• Modify download_video in video_describer.py to include a timeout parameter in the requests.get call (default: 10 seconds).
• Update test_download_video in tests/test_video_describer.py to validate timeout behavior:
  • Mock a requests.get timeout and verify graceful error handling (e.g., exception raised/logged).
  • Confirm the timeout value is passed correctly in the HTTP request.
• Ensure get_video_descriptions propagates timeout configurations to download_video if applicable.
• Validate via integration testing:
  • Use a non-responsive test URL to confirm the request aborts after the specified timeout.
  • Verify the default timeout works as expected unless overridden.