chore: clean up redundant comments across Go backend and Flutter sources

lib/widgets/animation_utils.dart

@@ -542,7 +542,7 @@ class ArtistScreenSkeleton extends StatelessWidget {
                               borderRadius: 4,
                             ),
                             const SizedBox(height: 8),
-                            // Mimics the small "In Library" badge pill.
+
                             const SkeletonBox(
                               width: 64,
                               height: 14,

lib/widgets/app_announcement_dialog.dart

@@ -121,10 +121,6 @@ Future<void> showAppAnnouncementDialog(
   required RemoteAnnouncement announcement,
   required VoidCallback onDismiss,
 }) {
-  // barrierDismissible is false so a stray tap outside the dialog can no longer
-  // close (and silently mark-as-seen) the notice. Dismissal — and the
-  // mark-as-seen side effect in onDismiss — only happens via the explicit close
-  // button or the CTA, both of which call onDismiss themselves.
   return showDialog<void>(
     context: context,
     barrierDismissible: false,

lib/widgets/audio_analysis_widget.dart

@@ -1646,7 +1646,6 @@ class _SpectrogramView extends StatelessWidget {
               },
             ),
           ),
-          // Intensity color legend (matches the spectrogram colormap).
           Padding(
             padding: const EdgeInsets.fromLTRB(40, 0, 10, 8),
             child: Row(
@@ -1731,7 +1730,6 @@ class _SpectrogramPainter extends CustomPainter {
     );
     if (plot.width <= 0 || plot.height <= 0) return;
 
-    // Spectrogram image.
     canvas.drawImageRect(
       image,
       Rect.fromLTWH(0, 0, image.width.toDouble(), image.height.toDouble()),
@@ -1760,7 +1758,6 @@ class _SpectrogramPainter extends CustomPainter {
       }
     }
 
-    // Time axis (X): 0 at the left, duration at the right.
     if (durationSec > 0) {
       final stepSec = _niceStepSec(durationSec);
       for (double ts = 0; ts <= durationSec + 0.001; ts += stepSec) {