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/Route.d.ts

@@ -0,0 +1,37 @@
+import { HTTPMethod } from './utils/constants.js';
+import { RouteHandler, RouteHandlerObject, RouteMatchCallback } from 'workbox-core/types.js';
+import './_version.js';
+/**
+ * A `Route` consists of a pair of callback functions, "match" and "handler".
+ * The "match" callback determine if a route should be used to "handle" a
+ * request by returning a non-falsy value if it can. The "handler" callback
+ * is called when there is a match and should return a Promise that resolves
+ * to a `Response`.
+ *
+ * @memberof workbox-routing
+ */
+declare class Route {
+    handler: RouteHandlerObject;
+    match: RouteMatchCallback;
+    method: HTTPMethod;
+    catchHandler?: RouteHandlerObject;
+    /**
+     * Constructor for Route class.
+     *
+     * @param {workbox-routing~matchCallback} match
+     * A callback function that determines whether the route matches a given
+     * `fetch` event by returning a non-falsy value.
+     * @param {workbox-routing~handlerCallback} handler A callback
+     * function that returns a Promise resolving to a Response.
+     * @param {string} [method='GET'] The HTTP method to match the Route
+     * against.
+     */
+    constructor(match: RouteMatchCallback, handler: RouteHandler, method?: HTTPMethod);
+    /**
+     *
+     * @param {workbox-routing-handlerCallback} handler A callback
+     * function that returns a Promise resolving to a Response
+     */
+    setCatchHandler(handler: RouteHandler): void;
+}
+export { Route };