phase-2: add shared platform interfaces and type contracts

src/app/shared/models/config/permissions.model.ts

@@ -0,0 +1,14 @@
+export interface PermissionDefinition {
+  key: string;
+  description?: string;
+}
+
+export interface RolePermissions {
+  role: string;
+  permissions: string[];
+}
+
+export interface PermissionsConfig {
+  definitions: PermissionDefinition[];
+  roles: RolePermissions[];
+}