fix(schema): fix migration ordering hazard and FK guard for table rebuild

Remove federated_id from addMissingColumns so it no longer races with
migrateDmChannelsFederatedId on installs that have canonical_pair_id.
Wrap the table rebuild in PRAGMA foreign_keys = OFF/ON with a transaction
so the DROP TABLE succeeds even when dm_members/dm_messages hold FK refs.

packages/server/src/db/migrate.ts

@@ -183,7 +183,6 @@ export function runMigrations(db: Database.Database): void {
     {
       name: 'dm_channels',
       columns: [
-        { name: 'federated_id', type: 'TEXT' },
         { name: 'owner_home_user_id', type: 'TEXT' },
         { name: 'owner_home_instance', type: 'TEXT' },
         { name: 'deleted_at', type: 'INTEGER' },
@@ -1494,8 +1493,11 @@ function migrateDmChannelsFederatedId(db: Database.Database): void {
   }
 
   if (hasOldCol && !hasNewCol) {
-    // Full table rebuild to rename column and add new columns in one atomic step
+    // Full table rebuild to rename column — disable FK enforcement during DROP
     console.log('Migrating: Renaming canonical_pair_id → federated_id in dm_channels and adding group DM columns...');
+    db.exec(`PRAGMA foreign_keys = OFF`);
+    try {
+      db.transaction(() => {
         db.exec(`
           CREATE TABLE dm_channels_new (
             id TEXT PRIMARY KEY,
@@ -1511,6 +1513,10 @@ function migrateDmChannelsFederatedId(db: Database.Database): void {
           DROP TABLE dm_channels;
           ALTER TABLE dm_channels_new RENAME TO dm_channels;
         `);
+      })();
+    } finally {
+      db.exec(`PRAGMA foreign_keys = ON`);
+    }
     db.exec(`DROP INDEX IF EXISTS idx_dm_canonical_pair`);
     db.exec(`CREATE UNIQUE INDEX IF NOT EXISTS idx_dm_federated ON dm_channels(federated_id) WHERE federated_id IS NOT NULL`);
     console.log('Migrating: dm_channels rename complete.');