Implement verified curriculum, video review, watch sessions, ledger safeguards, and remove demo data

backend/app/Services/VideoService.php

@@ -21,10 +21,13 @@ class VideoService
      */
     public static function ensureSchema(): void
     {
+        // Schema is installed by backend/scripts/run_migrations.php.
+        // Legacy request-time DDL remains below only as historical reference.
+        return;
+        /*
         if (self::$schemaChecked) {
             return;
         }
-
         try {
             // Check if storage_type column exists
             $cols = Database::select("SHOW COLUMNS FROM lessons LIKE 'storage_type'");
@@ -91,6 +94,7 @@ class VideoService
         } catch (\Throwable $e) {
             error_log("VideoService schema ensure note: " . $e->getMessage());
         }
+        */
     }
 
     /**