feat(api): add batches module for batch processing management
- Implement POST /api/batch endpoint for multipart file uploads
- Add GET /api/batch/{batchId}/status for real-time progress tracking
- Support batch cancellation, retry, and ZIP download generation
- Include comprehensive validation and quota checking
- Add progress broadcasting integration with WebSocket gateway
- Implement batch lifecycle management (create, process, complete)
Resolves requirements §29, §32, §73-§74 for batch processing API.
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Co-Authored-By: Claude <noreply@anthropic.com>
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