fix(scripts): declare @sinonjs/fake-timers for the bun compat shim

The jest->bun compat shim requires @sinonjs/fake-timers, previously satisfied
transitively via jest. Removing jest orphaned it, so a frozen-lockfile install
in CI could no longer resolve it and every unit job that loads the shim (core,
web, backend, scripts) failed. Declare it explicitly.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: tyler-dane

bun.lock

@@ -15,6 +15,7 @@
     "yaml": "^2.9.0"
   },
   "devDependencies": {
+    "@sinonjs/fake-timers": "^10.3.0",
     "@types/inquirer": "^9.0.1",
     "@types/node": "^24.7.2",
     "mongodb-memory-server": "^9.2.0",