refactor(client): split feature chunks and polish environment ui

- lazy-load route pages and add entity-based manual chunking in Vite

- prevent environment pages from crashing when legacy records miss data

- fix sidebar toggle chevron direction and make env forms full width

client/vite.config.ts

@@ -25,6 +25,49 @@ export default defineConfig({
     __APP_VERSION__: JSON.stringify(APP_VERSION),
   },
   plugins: [react()],
+  build: {
+    rollupOptions: {
+      output: {
+        manualChunks(id) {
+          if (!id.includes('/client/src/') && !id.includes('/node_modules/')) {
+            return;
+          }
+
+          if (id.includes('/node_modules/lucide-react')) {
+            return 'icons';
+          }
+          if (id.includes('/node_modules/monaco-editor') || id.includes('/node_modules/@monaco-editor')) {
+            return 'editor';
+          }
+          if (id.includes('/node_modules/')) {
+            return 'vendor';
+          }
+
+          if (id.includes('/src/pages/environment/')) {
+            return 'environments';
+          }
+          if (id.includes('/src/pages/scenario/')) {
+            return 'scenarios';
+          }
+          if (id.includes('/src/pages/run/')) {
+            return 'runs';
+          }
+          if (id.includes('/src/pages/snippet/')) {
+            return 'snippets';
+          }
+          if (id.includes('/src/pages/credential/')) {
+            return 'credentials';
+          }
+          if (id.includes('/src/pages/session/')) {
+            return 'sessions';
+          }
+          if (id.includes('/src/api/')) {
+            return 'api';
+          }
+        },
+      },
+    },
+  },
   server: {
     proxy: {
       '/environments': 'http://localhost:13000',