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/014_add_command_source.up.sql

@@ -3,15 +3,22 @@
 -- 'system' = automatically triggered by system operations (scans, installs, etc)
 
 ALTER TABLE agent_commands
-ADD COLUMN source VARCHAR(20) DEFAULT 'manual' NOT NULL;
+ADD COLUMN IF NOT EXISTS source VARCHAR(20) DEFAULT 'manual' NOT NULL;
 
 -- Add check constraint to ensure valid source values
-ALTER TABLE agent_commands
-ADD CONSTRAINT agent_commands_source_check
-CHECK (source IN ('manual', 'system'));
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM pg_constraint WHERE conname = 'agent_commands_source_check'
+    ) THEN
+        ALTER TABLE agent_commands
+        ADD CONSTRAINT agent_commands_source_check
+        CHECK (source IN ('manual', 'system'));
+    END IF;
+END $$;
 
 -- Add index for filtering commands by source
-CREATE INDEX idx_agent_commands_source ON agent_commands(source);
+CREATE INDEX IF NOT EXISTS idx_agent_commands_source ON agent_commands(source);
 
 -- Update comment
 COMMENT ON COLUMN agent_commands.source IS 'Command origin: manual (user-initiated) or system (auto-triggered)';