Ported the legacy '/hosted_file/hash/{hash}' endpoint to the V3 actions router.
The new endpoint '/v3/action/hosted_file/hash/{hosted_file_hash}' supports:
- ID Vision: returns random string IDs instead of internal integers
- Local Check: verifies physical file existence on disk (check_for_local=True)
- Deduplication: enables frontend to check for existing files before upload
Also added PROJECT document for AE Hosted Files migration tracking.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Hardened StreamingResponse headers to use RFC 6266 filename* parameter with UTF-8 encoding. This prevents the latin-1 codec crash when filenames contain non-ASCII characters like smart quotes.
- Adds GET /v3/action/hosted_file/hash/{sha256}/download for direct content-addressable storage access.
- Updates V3 authentication dependencies to support 'api_key' in the query parameter (alias 'api_key').
- Implements auth_method: 'api_key' for machine-to-machine requests that provide a valid key but no user/account context.
- Updates GUIDE__V3_FRONTEND_API.md with the new endpoint and auth options.
- Updates download_file_action to automatically resolve container IDs (like event_file) to the underlying hosted_file.
- Updates GUIDE__V3_FRONTEND_API.md to document the 'ID Vision' standard for downloads.
- Resolves 404 errors observed when frontend passed event_file IDs to the hosted_file download endpoint.
