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/ajv/dist/vocabularies/applicator/not.js

@@ -0,0 +1,26 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const util_1 = require("../../compile/util");
+const def = {
+    keyword: "not",
+    schemaType: ["object", "boolean"],
+    trackErrors: true,
+    code(cxt) {
+        const { gen, schema, it } = cxt;
+        if ((0, util_1.alwaysValidSchema)(it, schema)) {
+            cxt.fail();
+            return;
+        }
+        const valid = gen.name("valid");
+        cxt.subschema({
+            keyword: "not",
+            compositeRule: true,
+            createErrors: false,
+            allErrors: false,
+        }, valid);
+        cxt.failResult(valid, () => cxt.reset(), () => cxt.error());
+    },
+    error: { message: "must NOT be valid" },
+};
+exports.default = def;
+//# sourceMappingURL=not.js.map