fixup: federation_audit_log DESC indexes + reserved M4 columns

- Add .desc() to all three federation_audit_log created_at indexes for
  reverse-chronological scans (PRD section 7.3)
- Add reserved nullable columns query_hash, outcome, bytes_out per
  TASKS.md M2-01 spec (written by M4, columns reserved now to avoid
  retroactive migration)
- Regenerate migration 0008 in-place (replaces 0008_careless_lake.sql
  with 0008_smart_lyja.sql containing DESC indexes + new columns)
- Update integration test: add reserved columns to CREATE TABLE in
  beforeAll; add 7th test for peer→grant cascade delete

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/db/drizzle/meta/_journal.json

@@ -61,8 +61,8 @@
     {
       "idx": 8,
       "version": "7",
-      "when": 1776821378331,
-      "tag": "0008_careless_lake",
+      "when": 1776822435828,
+      "tag": "0008_smart_lyja",
       "breakpoints": true
     }
   ]