feat(database): update passwordHash length and add migration snapshot

Increase `passwordHash` field length to 100 in the `users` schema to accommodate larger hashes. Add migration snapshot `0005_snapshot.json` to capture database state changes.

backend/.migrations/0005_perpetual_silverclaw.sql

@@ -0,0 +1 @@
+ALTER TABLE "users" ALTER COLUMN "password_hash" SET DATA TYPE varchar(100);

backend/.migrations/meta/_journal.json

@@ -36,6 +36,13 @@
       "when": 1768417827439,
       "tag": "0004_cheerful_dakota_north",
       "breakpoints": true
+    },
+    {
+      "idx": 5,
+      "version": "7",
+      "when": 1768420201679,
+      "tag": "0005_perpetual_silverclaw",
+      "breakpoints": true
     }
   ]
 }