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/validation/const.js

@@ -0,0 +1,25 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const codegen_1 = require("../../compile/codegen");
+const util_1 = require("../../compile/util");
+const equal_1 = require("../../runtime/equal");
+const error = {
+    message: "must be equal to constant",
+    params: ({ schemaCode }) => (0, codegen_1._) `{allowedValue: ${schemaCode}}`,
+};
+const def = {
+    keyword: "const",
+    $data: true,
+    error,
+    code(cxt) {
+        const { gen, data, $data, schemaCode, schema } = cxt;
+        if ($data || (schema && typeof schema == "object")) {
+            cxt.fail$data((0, codegen_1._) `!${(0, util_1.useFunc)(gen, equal_1.default)}(${data}, ${schemaCode})`);
+        }
+        else {
+            cxt.fail((0, codegen_1._) `${schema} !== ${data}`);
+        }
+    },
+};
+exports.default = def;
+//# sourceMappingURL=const.js.map