fix(database): B-1 schema integrity and migration fixes

- Fix migration 024 self-insert and bad column reference (F-B1-1, F-B1-2)
  Uses existing enabled/auto_run columns instead of non-existent deprecated
- Abort server on migration failure instead of warning (F-B1-11)
  main.go now calls log.Fatalf, prints [INFO] only on success
- Fix migration 018 scanner_config filename suffix (F-B1-3)
  Renumbered to 027 with .up.sql suffix
- Remove GRANT to non-existent role in scanner_config (F-B1-4)
- Resolve duplicate migration numbers 009 and 012 (F-B1-13)
  Renamed to 009b and 012b for unique lexical sorting
- Add IF NOT EXISTS to all non-idempotent migrations (F-B1-15)
  Fixed: 011, 012, 017, 023, 023a
- Replace N+1 dashboard stats loop with GetAllUpdateStats (F-B1-6)
  Single aggregate query replaces per-agent loop
- Add composite index on agent_commands(status, sent_at) (F-B1-5)
  New migration 028 with partial index for timeout service
- Add background refresh token cleanup goroutine (F-B1-10)
  24-hour ticker calls CleanupExpiredTokens
- ETHOS log format in migration runner (no emojis)

All 55 tests pass (41 server + 14 agent). No regressions.
See docs/B1_Fix_Implementation.md and DEV-025 through DEV-028.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

aggregator-server/internal/database/migrations/012b_create_admin_user.up.sql

@@ -0,0 +1,10 @@
+-- Create admin user from environment configuration
+-- This migration reads the admin credentials from environment variables
+-- and creates the initial admin user in the database
+
+-- Note: This is a placeholder migration that will be executed by the application
+-- The actual user creation logic is handled in the main application startup
+-- to allow for proper password hashing and error handling
+
+-- The admin user creation is handled by the application during startup
+-- This migration file exists for version tracking purposes