fix: manual mapping UI and [S] tag consistency

- Fix manual mapping track selection visual feedback (use accent color + background)
- Clear all playlist caches after manual mapping (matched, ordered, items)
- Strip [S] suffix from titles/artists/albums when searching for lyrics
- Add [S] suffix to artist and album names when song has [S] for consistency
- Ensures external tracks are clearly marked across all metadata fields

All 225 tests pass.

allstarr/wwwroot/index.html

@@ -2005,10 +2005,12 @@
             // Remove selection from all tracks
             document.querySelectorAll('#map-search-results .track-item').forEach(el => {
                 el.style.border = '2px solid transparent';
+                el.style.background = '';
             });
             
             // Highlight selected track
-            element.style.border = '2px solid var(--primary)';
+            element.style.border = '2px solid var(--accent)';
+            element.style.background = 'var(--bg-tertiary)';
             
             // Store selected ID and enable save button
             document.getElementById('map-selected-jellyfin-id').value = jellyfinId;