Update all test files to import from canonical module locations:
- Integration tests: orders, inventory, messages, invoices
- Unit tests: services and models
- Fixtures: customer, vendor, message fixtures
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
- Refactor messaging API endpoints for admin, shop, and vendor
- Add message-specific exceptions (ConversationNotFoundException, etc.)
- Enhance messaging service with additional helper methods
- Add comprehensive test fixtures for messaging
- Add integration tests for admin and vendor messaging APIs
- Add unit tests for messaging and attachment services
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
