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/lib/compile/validate/applicability.ts

@@ -0,0 +1,22 @@
+import type {AnySchemaObject} from "../../types"
+import type {SchemaObjCxt} from ".."
+import type {JSONType, RuleGroup, Rule} from "../rules"
+
+export function schemaHasRulesForType(
+  {schema, self}: SchemaObjCxt,
+  type: JSONType
+): boolean | undefined {
+  const group = self.RULES.types[type]
+  return group && group !== true && shouldUseGroup(schema, group)
+}
+
+export function shouldUseGroup(schema: AnySchemaObject, group: RuleGroup): boolean {
+  return group.rules.some((rule) => shouldUseRule(schema, rule))
+}
+
+export function shouldUseRule(schema: AnySchemaObject, rule: Rule): boolean | undefined {
+  return (
+    schema[rule.keyword] !== undefined ||
+    rule.definition.implements?.some((kwd) => schema[kwd] !== undefined)
+  )
+}