fix: write DurationSeconds to SQL after replace-audio vault swap

DeepDrftAPI/Services/UnifiedTrackService.cs

@@ -168,12 +168,13 @@ public class UnifiedTrackService
 
     /// <summary>
     /// Replace an existing track's audio in place: look up the SQL row, swap only the vault bytes
-    /// keyed by its EntryKey, then regenerate both waveform datums from the new audio. Track id,
-    /// EntryKey, release membership, track number, and all metadata are preserved — nothing in SQL
-    /// is written. The waveform regen is best-effort (a missing datum renders as a flat seekbar /
-    /// blank visualizer downstream), so a datum failure is logged and swallowed rather than failing
-    /// the replace. No release-cardinality cascade applies: the track count is unchanged, so the
-    /// single-track-Mix case stays intact.
+    /// keyed by its EntryKey, regenerate both waveform datums from the new audio, then write the
+    /// new duration to SQL. Track id, EntryKey, release membership, track number, and all other
+    /// metadata are preserved. The waveform regen is best-effort (a missing datum renders as a flat
+    /// seekbar / blank visualizer downstream), so a datum failure is logged and swallowed rather than
+    /// failing the replace. The duration write is not best-effort — a failure is surfaced so derived
+    /// aggregates (e.g. MixRuntimeSeconds) do not silently go stale. No release-cardinality cascade
+    /// applies: the track count is unchanged, so the single-track-Mix case stays intact.
     /// </summary>
     public async Task<Result> ReplaceAudioAsync(long trackId, string tempFilePath, CancellationToken ct)
     {
@@ -212,6 +213,20 @@ public class UnifiedTrackService
             _logger.LogError(ex, "ReplaceAudioAsync: waveform regen failed for {EntryKey}; replace unaffected.", entryKey);
         }
 
+        // Write the new duration to SQL. The vault bytes are already swapped, so this is the
+        // authoritative metadata update for the replace. A failure here is surfaced (unlike the
+        // best-effort waveform regen above) because a stale DurationSeconds silently corrupts
+        // derived aggregates (e.g. MixRuntimeSeconds on the home stats endpoint).
+        var durationWrite = await _sqlTrackService.UpdateDuration(trackId, newAudio.Duration, ct);
+        if (!durationWrite.Success)
+        {
+            var error = durationWrite.Messages.FirstOrDefault()?.Message ?? "Unknown error";
+            _logger.LogError(
+                "ReplaceAudioAsync: vault swap succeeded but SQL duration update failed for track {TrackId} ({EntryKey}): {Error}",
+                trackId, entryKey, error);
+            return Result.CreateFailResult("Audio replaced but duration metadata could not be updated.");
+        }
+
         return Result.CreatePassResult();
     }