Fix image-to-text service stalling on invalid images (#145)

* Fix image-to-text service stalling on invalid images (#144)

The service was retrying forever when encountering missing, corrupt, or
oversized images. This fix adds graceful error handling with proper
failure notifications.

Changes:
- Add errors.py with PermanentError/TransientError classification
- Add image validation (file exists, size < 10MB, valid image format)
- Implement retry logic with exponential backoff (5s, 10s, 20s) for
  transient errors only
- Add failure_sender to notify Rails of permanent failures (status=5)
- Add retry_count column to job queue with migration support
- Remove failed jobs from queue instead of infinite retry

Test coverage:
- 111 unit tests (including new error handling tests)
- 7 integration tests (including missing/corrupt image tests)
- Manual Docker testing confirmed fix works end-to-end

Closes #144

* Bump version to 2.0.2

* Add release workflow for version tags

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Co-authored-by: Jeremy Watt <neonwatty@Jeremys-Mac-mini.local>

Merge pull request #139 from neonwatty/feature/drag-drop-image-upload

Fix VERSION file path resolution for Docker containers

Merge pull request #139 from neonwatty/feature/drag-drop-image-upload

Fix VERSION file path resolution for Docker containers

Merge pull request #130 from neonwatty/feature/bulk-generation-planning

Feature/bulk generation planning

Foundation phase complete

Merge pull request #99 from neonwatty/readme-updates

first push

Update CHANGELOG.md

Merge pull request #27 from neonwatty/docker-build

docker-build yaml added

trigger

Merge pull request #9 from neonwatty/index_delta

Index delta