fix(auth): add account, session, and verification schemas; make passwordHash nullable

Backend/drizzle/0013_users_password_hash_nullable.sql

@@ -0,0 +1 @@
+ALTER TABLE "users" ALTER COLUMN "password_hash" DROP NOT NULL;

Backend/drizzle/meta/_journal.json

@@ -92,6 +92,13 @@
       "when": 1770740394562,
       "tag": "0012_natural_daredevil",
       "breakpoints": true
+    },
+    {
+      "idx": 13,
+      "version": "7",
+      "when": 1770800000000,
+      "tag": "0013_users_password_hash_nullable",
+      "breakpoints": true
     }
   ]
-}
+}