Publish patch notes to GitHub changelog surfaces

## Summary
Push patch note content to GitHub releases or discussions for better changelog visibility.

## Acceptance Criteria
1. Supabase tracks GitHub release/discussion identifiers for each patch note.
2. Publisher module authenticates with stored GitHub credentials and creates releases/discussions.
3. API endpoint triggers publishing and persists returned metadata.
4. Patch note UI adds "Publish to GitHub" control with status and links.
5. Documentation outlines required GitHub scopes, API usage, and error handling expectations.
6. Playwright tests cover publishing to GitHub (using mocked API responses) and surface status feedback states.

## Notes
- Consider background retries for failed GitHub calls.
- Reference the GitHub Releases REST API for supported fields and workflows: https://docs.github.com/en/rest/releases/releases?apiVersion=2022-11-28

Start by mapping the Supabase patch-note records, publisher module, API endpoint, patch note UI, and Playwright test area named in the issue. Read the GitHub Releases REST API documentation and determine how mocked responses cover success, errors, and status feedback. Done means identifiers and returned metadata persist, publishing is triggered, the UI exposes status and links, documentation covers scopes and errors, and Playwright tests pass.

Written by the indexing model from the issue text.