Add sync error logging, extend error flash, fix unload saves

- Log workforce sync errors to backend stdout so they appear in docker logs
- Extend error flash from 5s to 15s so errors are readable
- Replace sendBeacon (POST-only) with keepalive fetch (PUT) on unload —
  sendBeacon was hitting 404s on all three unload saves

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/node_modules/workbox-routing/registerRoute.d.ts

@@ -0,0 +1,24 @@
+import { RouteHandler, RouteMatchCallback } from 'workbox-core/types.js';
+import { Route } from './Route.js';
+import { HTTPMethod } from './utils/constants.js';
+import './_version.js';
+/**
+ * Easily register a RegExp, string, or function with a caching
+ * strategy to a singleton Router instance.
+ *
+ * This method will generate a Route for you if needed and
+ * call {@link workbox-routing.Router#registerRoute}.
+ *
+ * @param {RegExp|string|workbox-routing.Route~matchCallback|workbox-routing.Route} capture
+ * If the capture param is a `Route`, all other arguments will be ignored.
+ * @param {workbox-routing~handlerCallback} [handler] A callback
+ * function that returns a Promise resulting in a Response. This parameter
+ * is required if `capture` is not a `Route` object.
+ * @param {string} [method='GET'] The HTTP method to match the Route
+ * against.
+ * @return {workbox-routing.Route} The generated `Route`.
+ *
+ * @memberof workbox-routing
+ */
+declare function registerRoute(capture: RegExp | string | RouteMatchCallback | Route, handler?: RouteHandler, method?: HTTPMethod): Route;
+export { registerRoute };