debug: log spotapi playlist page structure to diagnose 0-track response

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/spotify_resolve.py

@@ -111,6 +111,13 @@ def resolve(sp_type, sp_id):
     tracks, skipped, offset = [], 0, 0
     while True:
         page  = pl.get_playlist_info(limit=100, offset=offset)
+        if offset == 0:
+            eprint(f'[spotapi] page0 type={type(page).__name__} keys={list(page.keys()) if isinstance(page, dict) else "list"}')
+            if isinstance(page, dict):
+                for k, v in page.items():
+                    eprint(f'[spotapi]   page0[{k!r}] = {type(v).__name__} {repr(v)[:120]}')
+            elif isinstance(page, list) and page:
+                eprint(f'[spotapi]   page0[0] = {repr(page[0])[:200]}')
         items = page if isinstance(page, list) else (page.get('items') or page.get('tracks') or [])
         if not items: break
         for item in items: