Add OCR enrichment pipeline for Myspace screenshots

[SahilKumar75]

Summary

Extend the Myspace capture flow so screenshots can be enriched with OCR text and searchable metadata.

Scope

• Define the payload passed from Myspace screenshot capture to the ML worker.
• Add worker-side OCR enrichment output fields for title hints, body text, tags, and confidence.
• Add an app-side integration plan for storing enriched fields on saved items.
• Keep OCR optional with a deterministic fallback when OCR is unavailable.

Acceptance Criteria

• The ML worker can return searchable enrichment metadata for screenshot-like input.
• Myspace storage has a clear field mapping for OCR output.
• Tests cover fallback behavior when OCR is missing.
• The PR avoids committing generated cache or coverage files.