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/@babel/plugin-transform-duplicate-keys/lib/index.js

@@ -0,0 +1,60 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+var _helperPluginUtils = require("@babel/helper-plugin-utils");
+var _core = require("@babel/core");
+function getName(key) {
+  if (_core.types.isIdentifier(key)) {
+    return key.name;
+  }
+  return key.value.toString();
+}
+var _default = exports.default = (0, _helperPluginUtils.declare)(api => {
+  api.assertVersion(7);
+  return {
+    name: "transform-duplicate-keys",
+    visitor: {
+      ObjectExpression(path) {
+        const {
+          node
+        } = path;
+        const plainProps = node.properties.filter(prop => !_core.types.isSpreadElement(prop) && !prop.computed);
+        const alreadySeenData = Object.create(null);
+        const alreadySeenGetters = Object.create(null);
+        const alreadySeenSetters = Object.create(null);
+        for (const prop of plainProps) {
+          const name = getName(prop.key);
+          let isDuplicate = false;
+          switch (prop.kind) {
+            case "get":
+              if (alreadySeenData[name] || alreadySeenGetters[name]) {
+                isDuplicate = true;
+              }
+              alreadySeenGetters[name] = true;
+              break;
+            case "set":
+              if (alreadySeenData[name] || alreadySeenSetters[name]) {
+                isDuplicate = true;
+              }
+              alreadySeenSetters[name] = true;
+              break;
+            default:
+              if (alreadySeenData[name] || alreadySeenGetters[name] || alreadySeenSetters[name]) {
+                isDuplicate = true;
+              }
+              alreadySeenData[name] = true;
+          }
+          if (isDuplicate) {
+            prop.computed = true;
+            prop.key = _core.types.stringLiteral(name);
+          }
+        }
+      }
+    }
+  };
+});
+
+//# sourceMappingURL=index.js.map