feat(platform): Basic user file management

[Pwuts]

• Resolves #9316
• Complements #9320

Changes 🏗️

• Implement basic storage/retrieval of user files
• Add .util.exceptions.NotFoundError
• dx: Add google-api-python-client-stubs as dev dependency

⚠️ Config change:

• Add USER_FILE_GCS_BUCKET_NAME secret

Checklist 📋

For code changes:

• [ ] I have clearly listed my changes in the PR description
• [ ] I have made a test plan
• [ ] I have tested my changes according to the test plan:
  • [ ] ...

For configuration changes:

• [ ] .env.example is updated or already compatible with my changes
• [ ] docker-compose.yml is updated or already compatible with my changes
• [x] I have included a list of my configuration changes in the PR description (under Changes)

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[github-actions[bot]]

This pull request has conflicts with the base branch, please resolve those so we can evaluate the pull request.

[AutoGPT-Agent]

Thank you for implementing the basic user file management functionality. The implementation looks well-structured with proper security considerations for user_id handling throughout the backend operations.

However, I cannot approve this PR for merging because the checklist in the PR description is incomplete:

1. None of the items in the "For code changes" section are checked off
2. You need to provide a test plan that details how you've tested these changes

The actual code changes look promising:

• Backend data layer with proper user_id validation for file operations
• Frontend API client integration for file management
• Database schema updates to track file ownership
• Clear documentation of the required configuration change (USER_FILE_GCS_BUCKET_NAME)

Please complete the checklist by checking off the items for code changes and providing a detailed test plan describing how you've verified that the file upload, retrieval, and management features work correctly. Once that's done, the PR can be reconsidered for merging.