Bring back the external API keys

Commit 0dbb13f removed the whole feature: the apikeys tab, the /ui/apikeys
routes, requireApiKey, the /api/v1 router, the ApiKey type, the better-sqlite3
dependency and UI_DB_FILE in the CLI and the installer. Only the untracked
awg-ui/API.md survived, so the README went on to claim there was no key-based
API at all.

Restores all of it: ui.db with the api_keys table, awgk_ key generation storing
only the SHA-256 and a display prefix, the JWT-guarded CRUD, and the /api/v1
router mounted before the JWT proxy on /api so the key auth is not swallowed.
The tab comes back as its own folder and the registry picks it up on its own.
UI_DB_FILE points at /etc/amnezia/amneziawg/ui.db, outside the install tree, so
reinstalling keeps the keys; a fresh install moves the old one aside with its
WAL sidecars.

better-sqlite3 takes the slot of jsonwebtoken, which arrived with the MA7
integration and has been unused since 068cab4 removed it.

One defect is not reproduced: the /api/v1 handlers called ctrl() without a
try/catch, and Express 4 does not catch async rejections, so a single request
with awg-ctrl down killed the panel process. They now answer 502 like proxy()
already did.

The API contract is documented in the README rather than linked: .gitignore
excludes every markdown but README.md, so awg-ui/API.md is not in the repo and
the link would break on a clone.

Checked against a running server: login, key create/list/delete, 400 on a bad
label, 401 without a JWT, "API key required" rather than "Unauthorized" on
/api/v1, "Invalid API key" for a deleted key, last_used updating, and all three
/api/v1 routes returning 502 with the process still alive.

awg-ui/package.json

@@ -12,14 +12,14 @@
   },
   "dependencies": {
     "axios": "^1.7.0",
-    "jsonwebtoken": "^9.0.0",
+    "better-sqlite3": "^12.10.0",
     "qrcode": "^1.5.0",
     "react": "^18.3.0",
     "react-dom": "^18.3.0"
   },
   "devDependencies": {
     "concurrently": "^9.0.0",
-    "@types/jsonwebtoken": "^9.0.0",
+    "@types/better-sqlite3": "^7.6.13",
     "@types/qrcode": "^1.5.0",
     "@types/express": "^4.17.0",
     "@types/node": "^22.0.0",