feat(dashboard): capabilities helper for role-aware UI shadowing

Pure-function module that mirrors crates/manager-core/src/authz.rs and
lets dashboard pages decide which create / edit / delete affordances to
render. Widens the vitest include so the truth-table test runs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/vitest.config.ts

@@ -9,7 +9,7 @@ import { defineConfig } from 'vitest/config';
 
 export default defineConfig({
 	test: {
-		include: ['src/lib/rhai/**/*.test.ts'],
+		include: ['src/lib/**/*.test.ts'],
 		environment: 'node'
 	}
 });