feat(database): add migration snapshot 0006_snapshot.json for schema updates

Capture extensive database schema changes, including new tables and updated relationships for better data management and integrity.

backend/.migrations/meta/_journal.json

@@ -43,6 +43,13 @@
       "when": 1768420201679,
       "tag": "0005_perpetual_silverclaw",
       "breakpoints": true
+    },
+    {
+      "idx": 6,
+      "version": "7",
+      "when": 1768423315172,
+      "tag": "0006_friendly_adam_warlock",
+      "breakpoints": true
     }
   ]
 }