feat: backfill null next_refresh_at in episode cache

internal/database/fix_20260526_episode_availability_backfill_next_refresh_at.go

@@ -0,0 +1,28 @@
+package database
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+)
+
+func init() {
+	registerDataFix(dataFix{
+		id: "20260526_episode_availability_backfill_next_refresh_at",
+		apply: func(ctx context.Context, sqlDB *sql.DB) error {
+			// Old caches could have next_refresh_at NULL (especially for airing shows with missing broadcast metadata),
+			// which can result in "never refresh again" behavior on the server.
+			_, err := sqlDB.ExecContext(ctx, `
+UPDATE episode_availability_cache
+SET next_refresh_at = datetime(CURRENT_TIMESTAMP, '+6 hours'),
+    updated_at = CURRENT_TIMESTAMP
+WHERE next_refresh_at IS NULL;
+`)
+			if err != nil {
+				return fmt.Errorf("backfill episode_availability_cache.next_refresh_at: %w", err)
+			}
+			return nil
+		},
+	})
+}
+