Fix TS build errors for Docker deploy

- Add vite-env.d.ts for ImportMeta.env type
- Bump tsconfig target/lib to ES2022 for Array.at()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/vite-env.d.ts

@@ -0,0 +1 @@
+/// <reference types="vite/client" />

tsconfig.json

@@ -1,9 +1,9 @@
 {
   "compilerOptions": {
-    "target": "ES2020",
+    "target": "ES2022",
     "useDefineForClassFields": true,
     "module": "ESNext",
-    "lib": ["ES2020", "DOM", "DOM.Iterable"],
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
     "skipLibCheck": true,
     "moduleResolution": "bundler",
     "allowImportingTsExtensions": true,