fix(imports): support weak storage moves

[therobbiedavis]

Summary

Allows imports from filesystems that cannot expose durable file or directory generation identity. A requested move now degrades to a verified copy that explicitly retains the source, instead of blocking the import, while durable-storage moves keep their existing source-retirement contract.

Fixes #852
Related to #827

Changes

Added

• Added a configurable weak-storage publication policy that defaults to CopyAndRetainSource and can be disabled.
• Added a compatibility publication journal and startup reconciliation for content-verified, additive-only imports.
• Added path-only registration leases and recovery ownership for primary audio files and unregistered companion files.
• Added root-folder and import UI disclosures that state weak-storage moves copy files and retain the source.

Changed

• Source capability checks now fall back to a content-only proof when durable filesystem identity is unsupported.
• Manual and automatic imports now report requested action, effective action, source disposition, and warning details.
• Primary audio files, tracked audio companions, and unregistered companions share the same publication-policy decision while retaining distinct recovery ownership.
• Deferred download cleanup downgrades remove_and_delete to non-destructive client removal when any imported source was retained.

Fixed

• Fixed NFS/CIFS imports being rejected solely because the storage cannot expose a durable file handle or inode generation.
• Fixed durable cross-volume companion publication recovery so registration state is committed before exact source retirement.
• Fixed weak-storage destination planning so an existing byte-identical but unowned pathname is not adopted as ownership proof.

Testing

• dotnet build listenarr.slnx --no-restore
• dotnet test listenarr.slnx --no-build --no-restore — 2,952 passed, 202 skipped
• Production service graph validation with ValidateScopes and ValidateOnBuild
• Focused publication, compatibility recovery, cleanup, companion, architecture, hosted-service, and migration-schema tests
• dotnet ef migrations has-pending-model-changes ... --no-build — no pending model changes
• dotnet format listenarr.slnx --no-restore --verify-no-changes --verbosity minimal
• npm run test:unit -- --run — 89 files, 597 tests passed
• npm run build, npm run lint:check, and npm run format:check
• Native Linux weak-publication/recovery and real cross-volume companion verification
• Docker Linux compatibility/recovery verification
• Real NFSv4 and CIFS/SMB3 publication verification for both primary and companion files

Notes

• The compatibility path is intentionally additive-only: it never overwrites an existing destination and never deletes the source.
• A weak-storage Move is therefore successful as Copy with SourceDisposition=Retained; this is surfaced before import in the UI and after import in API/job history.
• The final Windows test run is on this commit. Linux, Docker, NFSv4, and CIFS/SMB3 checks were run during implementation; a final full-source Docker mount was not repeated because the execution environment blocked exposing the repository read-write to an external container.