docs(schema): comment CHECK invariant on peer_approval_requests

drizzle's snapshot does not encode SQL-level CHECK constraints. Without
this comment, a future migration that recreates the table for unrelated
reasons would silently drop the (direction='inbound' → hmac_secret
NOT NULL) invariant.

packages/server/src/db/schema.ts

@@ -377,6 +377,11 @@ export const federationPeers = sqliteTable('federation_peers', {
   approvalToken: text('approval_token'),
 });
 
+// SQL-level CHECK constraint enforces (direction='inbound' → hmac_secret NOT NULL).
+// See packages/server/drizzle/0003_brave_inhumans.sql. drizzle-kit cannot represent
+// CHECK constraints in its snapshot, so any future migration that recreates this
+// table MUST re-add the CHECK clause by hand. The snapshot WILL silently drop it
+// otherwise.
 export const peerApprovalRequests = sqliteTable('peer_approval_requests', {
   id: text('id').primaryKey(),
   origin: text('origin').notNull(),