Refactor: ATProto Repository Storage with Indigo Carstore Integration

- Remove blob storage from repository interface and implementation
- Add GORM integration for better database management
- Integrate Indigo's carstore for proper CAR file storage
- Update repository wrapper to use external blockstore
- Add comprehensive test infrastructure with test database setup
- Add test environment configuration example
- Update dependencies to include required Indigo and IPFS packages
- Fix repository record operations to work without inline value storage
- Add proper error handling and migrations for carstore integration

This refactoring aligns the repository storage with ATProto standards by:
1. Using Indigo's carstore for efficient CAR file management
2. Removing custom blob storage in favor of standard IPFS blockstore
3. Improving test infrastructure for better integration testing

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Co-Authored-By: Claude <noreply@anthropic.com>