Lyrics and favorites improvements

- Fix unsynced lyrics displaying all at 0:00 by omitting Start field
- Improve LRC parsing with fuzzy search and synced lyrics preference
- Add DeleteAsync to proxy service for proper auth forwarding
- Support both /UserFavoriteItems and /Users/{userId}/FavoriteItems routes
- Fix favorite endpoints to properly forward authentication
- Add comprehensive logging for debugging
- Extend Spotify sync backward search window to 24 hours

allstarr.Tests/JellyfinProxyServiceTests.cs

@@ -85,7 +85,7 @@ public class JellyfinProxyServiceTests
     }
 
     [Fact]
-    public async Task GetJsonAsync_IncludesAuthHeader()
+    public async Task GetJsonAsync_WithoutClientHeaders_SendsNoAuth()
     {
         // Arrange
         HttpRequestMessage? captured = null;
@@ -102,13 +102,10 @@ public class JellyfinProxyServiceTests
         // Act
         await _service.GetJsonAsync("Items");
 
-        // Assert
+        // Assert - Should NOT include auth when no client headers provided
         Assert.NotNull(captured);
-        Assert.True(captured!.Headers.Contains("Authorization"));
-        var authHeader = captured.Headers.GetValues("Authorization").First();
-        Assert.Contains("MediaBrowser", authHeader);
-        Assert.Contains(_settings.ApiKey!, authHeader);
-        Assert.Contains(_settings.ClientName!, authHeader);
+        Assert.False(captured!.Headers.Contains("Authorization"));
+        Assert.False(captured.Headers.Contains("X-Emby-Authorization"));
     }
 
     [Fact]