## Summary
- add `GET /api/v1/datasets/:dataset_id/tags`
- add `PUT /api/v1/datasets/:dataset_id/tags`
- implement dataset tag listing and rename flow
- align rename tag validation and response shape with the Python API
- add handler and service tests for dataset tags
## Routes
- `GET /api/v1/datasets/:dataset_id/tags`
- `PUT /api/v1/datasets/:dataset_id/tags`
## Test
- Run specific tests for dataset tags:
```
go test -v ./internal/service ./internal/handler -run 'TestDatasetServiceListTags|TestDatasetServiceRenameTag|TestDatasetsHandlerListTags|TestDatasetsHandlerRenameTag'
```
- Run all tests for service and handler to verify no regressions:
```
go test ./internal/service ./internal/handler
```
- use curl cmd to test
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