fix(migrations): explicit id + enum cast for 0024 backfill

- mesh.topic.id has no PG-side default (drizzle $defaultFn is ORM-only)
- mesh.topic_member.role needs an explicit cast to the enum type

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/db/migrations/0024_general_topic_backfill.sql

@@ -9,8 +9,13 @@
 -- Idempotent — safe to re-run. The unique indices on (mesh_id, name) and
 -- (topic_id, member_id) make the inserts no-ops on the second pass.
 
-INSERT INTO mesh.topic (mesh_id, name, description, visibility)
+-- mesh.topic.id has no Postgres-side default (drizzle's $defaultFn runs
+-- only via the ORM), so generate a 32-char lowercase-hex id from a v4
+-- UUID with dashes stripped. gen_random_uuid is built into Postgres 13+
+-- so no pgcrypto extension required.
+INSERT INTO mesh.topic (id, mesh_id, name, description, visibility)
 SELECT
+  replace(gen_random_uuid()::text, '-', ''),
   m.id,
   'general',
   'Default mesh-wide channel. Every member can read and post.',
@@ -26,7 +31,7 @@ INSERT INTO mesh.topic_member (topic_id, member_id, role)
 SELECT
   t.id,
   mm.id,
-  CASE WHEN m.owner_user_id = mm.user_id THEN 'lead' ELSE 'member' END
+  (CASE WHEN m.owner_user_id = mm.user_id THEN 'lead' ELSE 'member' END)::mesh.topic_member_role
 FROM mesh.topic t
 JOIN mesh.mesh m   ON m.id = t.mesh_id
 JOIN mesh.member mm ON mm.mesh_id = t.mesh_id AND mm.revoked_at IS NULL