Add safe preview, marker protection and bounded scans

[Serph91P]

Summary

• add a metadata-only TheIntroDB preview task
• use the same repository read implementation and library filtering for Preview and Apply
• open Preview SQLite through a fresh immutable read-only session without schema initialization or sidecar writes
• checkpoint legacy WAL state and use DELETE journaling before immutable Preview reads
• suppress Preview configuration migration and anonymous usage reporting
• protect complete and partial existing intro and credits markers by default
• add opt-in ReplaceExistingMarkers with durable per-chapter ownership tokens
• remove at most one exact host chapter for each matching ownership ledger entry
• never adopt or remove legacy, native, manual or foreign chapters based only on name or timestamp
• preserve unrelated and duplicate Emby chapters
• add an exact per-scan lookup budget and stop immediately after the first HTTP 429
• keep on-demand fetch, preview segments, replacement and anonymous reporting disabled by default

Preview writes operational logs for observability. It does not write plugin configuration, segment or ownership data, Emby chapters, or anonymous analytics.

Verification

• clean Release build: 0 errors, 0 warnings
• tests: 20 passed
• vulnerable package audit: no findings
• Gitleaks 8.30.1: no leaks
• git diff --check: clean
• no typographic en dash or em dash characters in changed C#, JavaScript or HTML files

Closes #22

[Pasithea0]

Reviewed 677e0a8 — both remaining points are resolved: Preview/Apply now share the same repository reads, and ReplaceExistingMarkers is opt-in and only ever removes durably owned chapters. Tests cover the ownership and read-only paths well. Resolves #22

[Serph91P]

Thanks for merging this. Could you please publish a new plugin release containing merge commit d2f86e3 when convenient? The latest available release is still v1.0.7.3, so a new signed-off release artifact is needed before the updated Preview and Apply workflow can be rolled out.

[Pasithea0]

Thanks for merging this. Could you please publish a new plugin release containing merge commit d2f86e3 when convenient? The latest available release is still v1.0.7.3, so a new signed-off release artifact is needed before the updated Preview and Apply workflow can be rolled out.

Yup, just crossing some other issues off in #25. https://github.com/TheIntroDB/emby-plugin/releases/tag/v1.0.8.0 is now available through GitHub and the Emby marketplace.