feat(allocation): implement resource allocation feature

- Add AllocationController with CRUD + bulk endpoints
- Add AllocationValidationService for capacity/estimate validation
- Add AllocationMatrixService for optimized matrix queries
- Add AllocationPolicy for authorization
- Add AllocationResource for API responses
- Add frontend allocationService and matrix UI
- Add E2E tests for allocation matrix (20 tests)
- Add unit tests for validation service and policies
- Fix month format conversion (YYYY-MM to YYYY-MM-01)

frontend/src/lib/stores/expertMode.ts

@@ -0,0 +1,32 @@
+import { writable } from 'svelte/store';
+
+const EXPERT_MODE_KEY = 'headroom.capacity.expertMode';
+
+function getInitialExpertMode(): boolean {
+  if (typeof localStorage === 'undefined') return false;
+
+  const stored = localStorage.getItem(EXPERT_MODE_KEY);
+  if (stored === 'true') return true;
+  if (stored === 'false') return false;
+  return false;
+}
+
+const expertModeWritable = writable<boolean>(getInitialExpertMode());
+
+if (typeof localStorage !== 'undefined') {
+  expertModeWritable.subscribe((value) => {
+    localStorage.setItem(EXPERT_MODE_KEY, String(value));
+  });
+}
+
+export const expertMode = {
+  subscribe: expertModeWritable.subscribe,
+};
+
+export function setExpertMode(value: boolean): void {
+  expertModeWritable.set(value);
+}
+
+export function toggleExpertMode(): void {
+  expertModeWritable.update((current) => !current);
+}