feat(config): add system configuration module (Phase 3)

Implement the complete erp-config crate with:
- Data dictionaries (CRUD + items management)
- Dynamic menus (tree structure with role filtering)
- System settings (hierarchical: platform > tenant > org > user)
- Numbering rules (concurrency-safe via PostgreSQL advisory_lock)
- Theme and language configuration (via settings store)
- 6 database migrations (dictionaries, menus, settings, numbering_rules)
- Frontend Settings page with 5 tabs (dictionary, menu, numbering, settings, theme)

Refactor: move RBAC functions (require_permission) from erp-auth to erp-core
to avoid cross-module dependencies.

Add 20 new seed permissions for config module operations.

apps/web/src/api/settings.ts

@@ -0,0 +1,25 @@
+import client from './client';
+
+export interface SettingInfo {
+  id: string;
+  scope: string;
+  scope_id?: string;
+  setting_key: string;
+  setting_value: unknown;
+}
+
+export async function getSetting(key: string, scope?: string, scopeId?: string) {
+  const { data } = await client.get<{ success: boolean; data: SettingInfo }>(
+    `/config/settings/${key}`,
+    { params: { scope, scope_id: scopeId } },
+  );
+  return data.data;
+}
+
+export async function updateSetting(key: string, settingValue: unknown) {
+  const { data } = await client.put<{ success: boolean; data: SettingInfo }>(
+    `/config/settings/${key}`,
+    { setting_value: settingValue },
+  );
+  return data.data;
+}