feat: [OCISDEV-900] Connect storageprovider with coordinator instead of driver

[LarsJurgensen]

Wire storageprovider and dataprovider to the upload coordinator. This is the final step that makes TUS, postprocessing, AV scanning, and session management driver-independent.

• storageprovider.InitiateFileUpload routes through coord.InitiateUpload instead of fs.InitiateUpload
• Dataprovider starts the postprocessing NATS consumer on the coordinator, not on the driver
• datatx.DataTX.Handler gains a coord argument alongside the driver; all three implementations (simple, spaces, tus) updated
• PUT uploads go through coord.Upload; TUS registers coord.UseIn instead of the driver's UseIn
• ComposableFS check in the TUS manager removed; the coordinator satisfies the tusd data store interface for every driver
• Decomposedfs no longer subscribes to PostprocessingFinished, PostprocessingStepFinished, RestartPostprocessing, CleanUpload; the coordinator owns those
• Decomposedfs keeps RevertRevision under a separate consumer group (<group>-revisions) so it gets its own copy without contending with the coordinator's group
• Both services gain an upload_directory config key; required for drivers with no local filesystem root

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[LukasHirt]

Two correctness regressions, one reachability concern, two cleanups.

Blocking:

1. TouchFile's create-only symlink leaks an orphaned node on a concurrent-create race (pkg/storage/utils/decomposedfs/tree/tree.go:175).
2. OC-FileId is now permanently omitted from TUS responses for newly-created files (pkg/rhttp/datatx/manager/tus/tus.go:216).

Worth a look:
3. This PR is what makes pkg/upload's postprocessing path live for the dataprovider — and that path has no guard against a node vanishing mid-postprocessing (internal/http/services/dataprovider/dataprovider.go:117).

Minor:
4. Doubled NATS subscriptions for combined decomposedfs+dataprovider deployments (same line).
5. getCoordinator duplicated near-verbatim with storageprovider.go:234 (internal/http/services/dataprovider/dataprovider.go:146).