feat(identities): backfill user_identities from better-auth account rows

Author: Ripwords

apps/dashboard/server/db/migrations/0009_backfill_user_identities_from_account.sql

@@ -0,0 +1,16 @@
+-- Opportunistic backfill: users who signed in with GitHub via better-auth
+-- get their user_identities row seeded automatically.
+
+INSERT INTO user_identities
+  (user_id, provider, external_id, external_handle, linked_at, last_verified_at)
+SELECT
+  a.user_id,
+  'github'::identity_provider,
+  a.account_id,
+  COALESCE(u.name, a.account_id),
+  NOW(),
+  NOW()
+FROM account a
+JOIN "user" u ON u.id = a.user_id
+WHERE a.provider_id = 'github'
+ON CONFLICT (provider, external_id) DO NOTHING;

apps/dashboard/server/db/migrations/meta/_journal.json

@@ -64,6 +64,13 @@
       "when": 1776968447311,
       "tag": "0008_solid_marauders",
       "breakpoints": true
+    },
+    {
+      "idx": 9,
+      "version": "7",
+      "when": 1776970200000,
+      "tag": "0009_backfill_user_identities_from_account",
+      "breakpoints": true
     }
   ]
 }