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/items2020.js

@@ -0,0 +1,30 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const codegen_1 = require("../../compile/codegen");
+const util_1 = require("../../compile/util");
+const code_1 = require("../code");
+const additionalItems_1 = require("./additionalItems");
+const error = {
+    message: ({ params: { len } }) => (0, codegen_1.str) `must NOT have more than ${len} items`,
+    params: ({ params: { len } }) => (0, codegen_1._) `{limit: ${len}}`,
+};
+const def = {
+    keyword: "items",
+    type: "array",
+    schemaType: ["object", "boolean"],
+    before: "uniqueItems",
+    error,
+    code(cxt) {
+        const { schema, parentSchema, it } = cxt;
+        const { prefixItems } = parentSchema;
+        it.items = true;
+        if ((0, util_1.alwaysValidSchema)(it, schema))
+            return;
+        if (prefixItems)
+            (0, additionalItems_1.validateAdditionalItems)(cxt, prefixItems);
+        else
+            cxt.ok((0, code_1.validateArray)(cxt));
+    },
+};
+exports.default = def;
+//# sourceMappingURL=items2020.js.map