style: gofmt fixes across api package

CI's golangci-lint run flagged three files; two pre-existed this
branch but the Plan 3 seedTrackWithFile struct-literal alignment
is new. Applying gofmt across all three keeps the lint baseline clean.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/api/library_fixtures_test.go

@@ -108,13 +108,13 @@ func seedTrackWithFile(t *testing.T, pool *pgxpool.Pool, albumID, artistID pgtyp
 		TrackNumber: &one,
 		DiscNumber:  nil,
 		// DurationMs: arbitrary non-zero; tests don't assert on it.
-		DurationMs:  int32(len(fileBody)),
-		FilePath:    path,
-		FileSize:    int64(len(fileBody)),
-		FileFormat:  strings.ToLower(ext),
-		Bitrate:     nil,
-		Mbid:        nil,
-		Genre:       nil,
+		DurationMs: int32(len(fileBody)),
+		FilePath:   path,
+		FileSize:   int64(len(fileBody)),
+		FileFormat: strings.ToLower(ext),
+		Bitrate:    nil,
+		Mbid:       nil,
+		Genre:      nil,
 	})
 	if err != nil {
 		t.Fatalf("UpsertTrack(%s): %v", title, err)