feat: add claw approval MVP with privileged broker

Implement Postgres-backed claw approval flow and integrate gateway methods for create/list/get/approve/reject/execute/audit. Add a minimal systemd-run privileged broker with bearer auth, strict scope and exact-command validation, dangerous-shell blocking, atomic once-grant consumption, and execution audit updates.

package.json

@@ -382,6 +382,7 @@
     "opusscript": "^0.1.1",
     "osc-progress": "^0.3.0",
     "pdfjs-dist": "^5.5.207",
+    "pg": "^8.20.0",
     "playwright-core": "1.58.2",
     "qrcode-terminal": "^0.12.0",
     "sharp": "^0.34.5",
@@ -400,6 +401,7 @@
     "@types/express": "^5.0.6",
     "@types/markdown-it": "^14.1.2",
     "@types/node": "^25.5.0",
+    "@types/pg": "^8.18.0",
     "@types/qrcode-terminal": "^0.12.2",
     "@types/ws": "^8.18.1",
     "@typescript/native-preview": "7.0.0-dev.20260312.1",