feat(app): add environment import/export and sidebar footer info

- add environment import/export API endpoints and client integration

- add environment export actions and toolbar import/export buttons in UI

- move theme switcher to sidebar bottom and show root package version

- switch snippet card menu icon to cog for consistent options affordance

client/vite.config.ts

@@ -1,14 +1,29 @@
 /// <reference types="vitest/config" />
 import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react';
+import fs from 'node:fs';
 import path from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { storybookTest } from '@storybook/addon-vitest/vitest-plugin';
 import { playwright } from '@vitest/browser-playwright';
 const dirname = typeof __dirname !== 'undefined' ? __dirname : path.dirname(fileURLToPath(import.meta.url));
+const rootPackageJsonPath = path.resolve(dirname, '../package.json');
+const APP_VERSION = (() => {
+  try {
+    const json = JSON.parse(fs.readFileSync(rootPackageJsonPath, 'utf8')) as {
+      version?: string;
+    };
+    return json.version ?? 'dev';
+  } catch {
+    return 'dev';
+  }
+})();
 
 // More info at: https://storybook.js.org/docs/next/writing-tests/integrations/vitest-addon
 export default defineConfig({
+  define: {
+    __APP_VERSION__: JSON.stringify(APP_VERSION),
+  },
   plugins: [react()],
   server: {
     proxy: {