Switch to bun and add deploy script

Update engines in package.json to bun, switch all justfile recipes from npm to bun, add scripts/deploy.sh for production deployment.

justfile

@@ -1,34 +1,31 @@
-# Default deploy destination
-deploy_dir := "/var/www/tietokonepaja-fi"
-
 # Start development server
 dev:
-    npm run dev
+    bun run dev
 
 # Build for production (with type-check and .htaccess copy)
 build:
-    npm run build
+    bun run build
 
 # Preview production build locally
 preview:
-    npm run preview
+    bun run preview
 
 # Build without type-checking
 build-only *args:
-    npm run build-only -- {{args}}
+    bun run build-only -- {{args}}
 
 # Type-check with vue-tsc
 type-check:
-    npm run type-check
+    bun run type-check
 
 # Lint and auto-fix
 lint:
-    npm run lint
+    bun run lint
 
 # Format source files with Prettier
 format:
-    npm run format
+    bun run format
 
-# Build and deploy dist to the given directory (default: /var/www/tietokonepaja-fi)
-deploy dest=deploy_dir: build
-    cp -r dist/. {{dest}}
+# Deploy using the deploy script
+deploy:
+    bash scripts/deploy.sh