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/jake/test/integration/jakelib/concurrent.jake.js

@@ -0,0 +1,113 @@
+
+namespace('concurrent', function () {
+  task('A', function () {
+    console.log('Started A');
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        console.log('Finished A');
+        resolve();
+      }, 200);
+    });
+  });
+
+  task('B', function () {
+    console.log('Started B');
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        console.log('Finished B');
+        resolve();
+      }, 50);
+    });
+  });
+
+  task('C', function () {
+    console.log('Started C');
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        console.log('Finished C');
+        resolve();
+      }, 100);
+    });
+  });
+
+  task('D', function () {
+    console.log('Started D');
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        console.log('Finished D');
+        resolve();
+      }, 300);
+    });
+  });
+
+  task('Ba', ['A'], function () {
+    console.log('Started Ba');
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        console.log('Finished Ba');
+        resolve();
+      }, 50);
+    });
+  });
+
+  task('Afail', function () {
+    console.log('Started failing task');
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        console.log('Failing B with error');
+        throw new Error('I failed');
+      }, 50);
+    });
+  });
+
+  task('simple1', ['A','B'], {concurrency: 2}, function () {
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        resolve();
+      }, 50);
+    });
+  });
+
+  task('simple2', ['C','D'], {concurrency: 2}, function () {
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        resolve();
+      }, 50);
+    });
+  });
+
+  task('seqconcurrent', ['simple1','simple2'], function () {
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        resolve();
+      }, 50);
+    });
+  });
+
+  task('concurrentconcurrent', ['simple1','simple2'], {concurrency: 2}, function () {
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        resolve();
+      }, 50);
+    });
+  });
+
+  task('subdep', ['A','Ba'], {concurrency: 2}, function () {
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        resolve();
+      }, 50);
+    });
+  });
+
+  task('fail', ['A', 'B', 'Afail'], {concurrency: 3}, function () {
+    return new Promise((resolve, reject) => {
+      setTimeout(() => {
+        resolve();
+      }, 50);
+    });
+  });
+
+});
+
+