Add Spotify lyrics sidecar service and integrate with prefetch

- Add spotify-lyrics-api container to docker-compose
- Update SpotifyLyricsService to use sidecar API
- Prefetch now tries Spotify lyrics first (using track ID), then LRCLib
- Add SPOTIFY_LYRICS_API_URL setting
- Sidecar handles sp_dc cookie authentication automatically

allstarr/Services/Lyrics/SpotifyLyricsService.cs

@@ -29,6 +29,7 @@ public class SpotifyLyricsService
     private readonly HttpClient _httpClient;
     
     private const string LyricsApiBase = "https://spclient.wg.spotify.com/color-lyrics/v2/track";
+    private bool _useSidecarApi = false;
     
     public SpotifyLyricsService(
         ILogger<SpotifyLyricsService> logger,
@@ -45,6 +46,11 @@ public class SpotifyLyricsService
         _httpClient = httpClientFactory.CreateClient();
         _httpClient.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0");
         _httpClient.DefaultRequestHeaders.Add("App-Platform", "WebPlayer");
+        
+        // Check if sidecar API is configured and available
+        _useSidecarApi = !string.IsNullOrEmpty(_settings.LyricsApiUrl) && 
+                         _settings.LyricsApiUrl != "http://spotify-lyrics:8080" || 
+                         _settings.Enabled;
     }
     
     /// <summary>
@@ -72,6 +78,64 @@ public class SpotifyLyricsService
             return cached;
         }
         
+        // Try sidecar API first if available
+        if (_useSidecarApi && !string.IsNullOrEmpty(_settings.LyricsApiUrl))
+        {
+            var sidecarResult = await GetLyricsFromSidecarAsync(spotifyTrackId);
+            if (sidecarResult != null)
+            {
+                await _cache.SetAsync(cacheKey, sidecarResult, TimeSpan.FromDays(30));
+                return sidecarResult;
+            }
+        }
+        
+        // Fall back to direct API call
+        return await GetLyricsDirectAsync(spotifyTrackId, cacheKey);
+    }
+    
+    /// <summary>
+    /// Gets lyrics from the sidecar spotify-lyrics-api service.
+    /// </summary>
+    private async Task<SpotifyLyricsResult?> GetLyricsFromSidecarAsync(string spotifyTrackId)
+    {
+        try
+        {
+            var url = $"{_settings.LyricsApiUrl}/?trackid={spotifyTrackId}&format=id3";
+            
+            _logger.LogDebug("Fetching lyrics from sidecar API: {Url}", url);
+            
+            var response = await _httpClient.GetAsync(url);
+            
+            if (!response.IsSuccessStatusCode)
+            {
+                _logger.LogDebug("Sidecar API returned {StatusCode} for track {TrackId}", 
+                    response.StatusCode, spotifyTrackId);
+                return null;
+            }
+            
+            var json = await response.Content.ReadAsStringAsync();
+            var result = ParseSidecarResponse(json, spotifyTrackId);
+            
+            if (result != null)
+            {
+                _logger.LogInformation("Got Spotify lyrics from sidecar for track {TrackId} ({LineCount} lines)", 
+                    spotifyTrackId, result.Lines.Count);
+            }
+            
+            return result;
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex, "Error fetching lyrics from sidecar API for track {TrackId}", spotifyTrackId);
+            return null;
+        }
+    }
+    
+    /// <summary>
+    /// Gets lyrics directly from Spotify's color-lyrics API.
+    /// </summary>
+    private async Task<SpotifyLyricsResult?> GetLyricsDirectAsync(string spotifyTrackId, string cacheKey)
+    {
         try
         {
             // Get access token
@@ -356,6 +420,63 @@ public class SpotifyLyricsService
         }
     }
     
+    /// <summary>
+    /// Parses the response from the sidecar spotify-lyrics-api service.
+    /// Format: {"error": false, "syncType": "LINE_SYNCED", "lines": [...]}
+    /// </summary>
+    private SpotifyLyricsResult? ParseSidecarResponse(string json, string trackId)
+    {
+        try
+        {
+            using var doc = JsonDocument.Parse(json);
+            var root = doc.RootElement;
+            
+            // Check for error
+            if (root.TryGetProperty("error", out var error) && error.GetBoolean())
+            {
+                _logger.LogDebug("Sidecar API returned error for track {TrackId}", trackId);
+                return null;
+            }
+            
+            var result = new SpotifyLyricsResult
+            {
+                SpotifyTrackId = trackId
+            };
+            
+            // Get sync type
+            if (root.TryGetProperty("syncType", out var syncType))
+            {
+                result.SyncType = syncType.GetString() ?? "LINE_SYNCED";
+            }
+            
+            // Parse lines
+            if (root.TryGetProperty("lines", out var lines))
+            {
+                foreach (var line in lines.EnumerateArray())
+                {
+                    var lyricsLine = new SpotifyLyricsLine
+                    {
+                        StartTimeMs = line.TryGetProperty("startTimeMs", out var start) 
+                            ? long.Parse(start.GetString() ?? "0") : 0,
+                        Words = line.TryGetProperty("words", out var words) 
+                            ? words.GetString() ?? "" : "",
+                        EndTimeMs = line.TryGetProperty("endTimeMs", out var end)
+                            ? long.Parse(end.GetString() ?? "0") : 0
+                    };
+                    
+                    result.Lines.Add(lyricsLine);
+                }
+            }
+            
+            return result;
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Error parsing sidecar API response");
+            return null;
+        }
+    }
+    
     private static int? ParseColorValue(JsonElement element)
     {
         if (element.ValueKind == JsonValueKind.Number)