feat: add Clear Cache & Rebuild button for playlists in Admin UI

- New endpoint: POST /api/admin/playlists/{name}/clear-cache
- Clears Redis cache keys (items, matched tracks, missing tracks)
- Deletes file caches
- Triggers automatic rebuild with latest code (includes Spotify IDs)
- Added prominent button in Admin UI playlist table
- Shows confirmation dialog with details of what will be cleared

allstarr/Controllers/AdminController.cs

@@ -935,6 +935,77 @@ public class AdminController : ControllerBase
         }
     }
     
+    /// <summary>
+    /// Clear cache and rebuild for a specific playlist
+    /// </summary>
+    [HttpPost("playlists/{name}/clear-cache")]
+    public async Task<IActionResult> ClearPlaylistCache(string name)
+    {
+        var decodedName = Uri.UnescapeDataString(name);
+        _logger.LogInformation("Clear cache & rebuild triggered for playlist: {Name}", decodedName);
+        
+        if (_matchingService == null)
+        {
+            return BadRequest(new { error = "Track matching service is not available" });
+        }
+        
+        try
+        {
+            // Clear all cache keys for this playlist
+            var cacheKeys = new[]
+            {
+                $"spotify:playlist:items:{decodedName}",      // Pre-built items cache
+                $"spotify:matched:ordered:{decodedName}",     // Ordered matched tracks
+                $"spotify:matched:{decodedName}",             // Legacy matched tracks
+                $"spotify:missing:{decodedName}"              // Missing tracks
+            };
+            
+            foreach (var key in cacheKeys)
+            {
+                await _cache.DeleteAsync(key);
+                _logger.LogDebug("Cleared cache key: {Key}", key);
+            }
+            
+            // Delete file caches
+            var safeName = string.Join("_", decodedName.Split(Path.GetInvalidFileNameChars()));
+            var filesToDelete = new[]
+            {
+                Path.Combine(CacheDirectory, $"{safeName}_items.json"),
+                Path.Combine(CacheDirectory, $"{safeName}_matched.json")
+            };
+            
+            foreach (var file in filesToDelete)
+            {
+                if (System.IO.File.Exists(file))
+                {
+                    System.IO.File.Delete(file);
+                    _logger.LogDebug("Deleted cache file: {File}", file);
+                }
+            }
+            
+            _logger.LogInformation("✓ Cleared all caches for playlist: {Name}", decodedName);
+            
+            // Trigger rebuild
+            await _matchingService.TriggerMatchingForPlaylistAsync(decodedName);
+            
+            // Invalidate playlist summary cache
+            InvalidatePlaylistSummaryCache();
+            
+            return Ok(new 
+            { 
+                message = $"Cache cleared and rebuild triggered for {decodedName}", 
+                timestamp = DateTime.UtcNow,
+                clearedKeys = cacheKeys.Length,
+                clearedFiles = filesToDelete.Count(System.IO.File.Exists)
+            });
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to clear cache for {Name}", decodedName);
+            return StatusCode(500, new { error = "Failed to clear cache", details = ex.Message });
+        }
+    }
+    
     /// <summary>
     /// Search Jellyfin library for tracks (for manual mapping)
     /// </summary>

allstarr/wwwroot/index.html

@@ -1331,6 +1331,7 @@
                             </td>
                             <td class="cache-age">${p.cacheAge || '-'}</td>
                             <td>
+                                <button onclick="clearPlaylistCache('${escapeJs(p.name)}')">Clear Cache & Rebuild</button>
                                 <button onclick="matchPlaylistTracks('${escapeJs(p.name)}')">Match Tracks</button>
                                 <button onclick="prefetchLyrics('${escapeJs(p.name)}')">Prefetch Lyrics</button>
                                 <button onclick="viewTracks('${escapeJs(p.name)}')">View</button>
@@ -1672,6 +1673,26 @@
             }
         }
         
+        async function clearPlaylistCache(name) {
+            if (!confirm(`Clear cache and rebuild for "${name}"?\n\nThis will:\n• Clear Redis cache\n• Delete file caches\n• Rebuild with latest Spotify IDs\n\nThis may take a minute.`)) return;
+            
+            try {
+                showToast(`Clearing cache for ${name}...`, 'info');
+                const res = await fetch(`/api/admin/playlists/${encodeURIComponent(name)}/clear-cache`, { method: 'POST' });
+                const data = await res.json();
+                
+                if (res.ok) {
+                    showToast(`✓ ${data.message} (Cleared ${data.clearedKeys} cache keys, ${data.clearedFiles} files)`, 'success', 5000);
+                    // Refresh the playlists table after a delay to show updated counts
+                    setTimeout(fetchPlaylists, 3000);
+                } else {
+                    showToast(data.error || 'Failed to clear cache', 'error');
+                }
+            } catch (error) {
+                showToast('Failed to clear cache', 'error');
+            }
+        }
+        
         async function matchPlaylistTracks(name) {
             try {
                 showToast(`Matching tracks for ${name}...`, 'success');