Fix /health/ready res.status bug + add comprehensive health endpoint tests

The readiness probe was crashing with 'res.status is not a function' because
asyncHandler(async (req, res) => {...}, 'health-ready') was called directly,
but asyncHandler's signature is (logError, fn, context) — first arg is the
logger, not the handler. The fix uses boundAsyncHandler like all other routes
in the file do.

Added 8 unit tests for both /health/live and /health/ready:
- live always 200 (liveness ≠ readiness)
- ready returns 503 when config/services/docker fail
- no 'res.status is not a function' crash when dependencies fail
- all 4 check keys present in response

Also added MONITORING_PUBLIC env var (defaults true) and the new health
endpoints to PUBLIC_ROUTES so k8s probes can hit them without auth.

dashcaddy-api/middleware.js

@@ -298,7 +298,11 @@ module.exports = function configureMiddleware(app, {
 
   const PUBLIC_ROUTES = [
     { path: '/health',                   exact: true },
+    { path: '/health/live',              exact: true },
+    { path: '/health/ready',             exact: true },
     { path: '/api/v1/health',            exact: true },
+    { path: '/api/v1/health/live',       exact: true },
+    { path: '/api/v1/health/ready',      exact: true },
     { path: '/probe/',                   prefix: true },
     { path: '/api/v1/tailscale/',        prefix: true },
     { path: '/api/v1/totp/config',        exact: true,  method: 'GET' },