…anifest detection (#2657)

#### What this PR does / why we need it

Docker manifest v2
(`application/vnd.docker.distribution.manifest.v2+json`) and Docker
manifest list
(`application/vnd.docker.distribution.manifest.list.v2+json`) were
excluded from `isOCICompliantManifest` / `IsOCICompliantMediaType` in
both `bindings/go/oci/internal/introspection` and
`bindings/go/transfer/internal`. This caused LocalBlob resources with
Docker manifest media types to silently bypass the OCI artifact upload
path when using `UploadAsOciArtifact` mode during transfer — they were
stored as plain local blobs instead.

The root cause was a TODO in both functions noting Docker manifests were
not yet supported. This PR resolves that TODO by adding the two Docker
distribution manifest media type constants (mirroring `oras-go/v2`'s
internal definitions, which are not importable) and extending the switch
statements to accept them.

#### Which issue(s) this PR fixes

Internal report: standard `docker manifest` transfer broken in v2
transfer path (`UploadAsOciArtifact` mode).

#### Testing

##### How to test the changes

```bash
# Unit tests (fast)
cd bindings/go/transfer && go test ./internal/... -run "TestIsOCICompliant|TestBuildGraphDefinition_Docker" -v
cd bindings/go/oci && go test ./internal/introspection/... -v

# Integration test (requires Docker)
cd bindings/go/transfer/integration && go test -v -run Test_Integration_TransferDockerManifestLocalBlob_CTFToOCI
```

##### Verification

- [x] I have added/updated tests for my changes (see [Test
Requirements](../CONTRIBUTING.md#test-requirements))
- [x] Tests pass locally (`task test` and `task test/integration` if
applicable)
- [ ] If touching multiple modules, `go work` is enabled (see `go.work`)
- [x] My changes do not decrease test coverage
- [ ] I have tested the changes locally by running `ocm`

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Signed-off-by: Jakob Möller <contact@jakob-moeller.com>