Track Spotify origin (liked/playlist/top); make top tracks opt-in; clean Ctrl+C

- Tag each Spotify track with its origin (liked / from_playlist / from_top,
  combinable) so genuinely-saved tracks are distinguishable from ones only
  surfaced by the top-tracks endpoint.
- Top tracks are no longer added by default (they inflated "missing" with
  unowned listening stats). --include-top pulls them as full objects so they
  carry an ISRC for real ID matching.
- On --spotify-full, prune Spotify rows that are neither liked nor in a
  playlist (top-only / orphaned), cleaning an existing DB in one pass.
- Cached-ingest fallback honours include_top and prunes too.
- In-place SQLite migration adds the new columns (no DB rebuild needed).
- Ctrl+C exits cleanly (130) with a message instead of a traceback;
  incremental progress is already committed, so re-run to continue.
- Surface origin breakdown in the fetch log, match summary, and GUI.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -84,6 +84,15 @@ because each source only touches what changed:
   liked songs are paged newest-first and stop at the newest one already stored;
   cover art downloads only when missing or its URL changed (`--spotify-full`
   forces a complete resync).
+  - Your library is **liked songs + playlist tracks**. The *top-tracks* endpoint
+    is **not** pulled by default (those are just listening stats, not saved
+    music, and would inflate "missing"). Add `--include-top` to pull them too —
+    they're fetched as full Spotify objects, so they carry an ISRC for real ID
+    matching like everything else.
+  - Each Spotify track records its **origin** (`liked` / `playlist` / `top`,
+    combinable). On a `--spotify-full` run, rows that are *only* there because
+    the top endpoint listed them (neither liked nor in a playlist) are pruned —
+    run `python main.py fetch --spotify-full` once to clean up an existing DB.
 - **Local** — only files whose mtime/size changed; deleted files are pruned.
 - **iTunes** — skipped entirely if the export's mtime is unchanged.
 - **MBID enrichment** — only still-unresolved tracks.