1. Implemented specialized 'from_hosted_file' action for Event Files.\n2. Fixed ValueError in Pydantic models by removing default/default_factory conflict.\n3. Hardened integer stripping to strictly enforce Vision Standards.\n4. Updated documentation for the new action route.
- Creates api_v3_actions_event_file.py with a specialized /upload endpoint.
- Handles physical storage (hosted_file), generic linking, and event association (event_file) in one request.
- Implements intelligent ID resolution to prevent duplicate event associations for the same physical file.
- Updates documentation in GUIDE__V3_FRONTEND_API.md.