Regenerate API models for file fields

[giordano-lucas]

Summary

• Regenerated internal/api/client.gen.go to align the models with the current OpenAPI schema.
• Updated file-bearing request and response models to use string fields instead of openapi_types.File.
• Expanded ValidationError to include the new optional ctx and input fields.

Testing

• Not run (generated code update only).
• Reviewed the diff to confirm the regenerated model fields match the schema changes.

[greptile-apps]

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