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/resolve/.claude/settings.local.json

@@ -0,0 +1,26 @@
+{
+  "permissions": {
+    "allow": [
+      "WebFetch(domain:github.com)",
+      "WebSearch",
+      "WebFetch(domain:raw.githubusercontent.com)",
+      "WebFetch(domain:api.github.com)",
+      "WebFetch(domain:www.npmjs.com)",
+      "Bash(tree:*)",
+      "Bash(find:*)",
+      "Bash(npm view:*)",
+      "Bash(node test/resolver_sync.js:*)",
+      "Bash(xxd:*)",
+      "Bash(npm info:*)",
+      "Bash(grep:*)",
+      "Bash(npm run submodule:update:*)",
+      "Bash(git rev-parse:*)",
+      "Bash(git -C test/list-exports diff packages/tests/fixtures/resolve-2/project/test/resolver/nested_symlinks/mylib/async.js)",
+      "Bash(gh run list:*)",
+      "Bash(ls:*)",
+      "Bash(tape test/homedir.js)",
+      "Bash(tape test/default_paths.js)",
+      "Bash(tape test/mock.js)"
+    ]
+  }
+}