chore: switch from npm to pnpm (#786)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

frontend/package.json

@@ -4,6 +4,7 @@
 	"private": true,
 	"type": "module",
 	"scripts": {
+		"preinstall": "npx only-allow pnpm",
 		"dev": "vite dev --port 3000",
 		"build": "vite build",
 		"preview": "vite preview --port 3000",
@@ -29,7 +30,6 @@
 		"@inlang/plugin-message-format": "^4.0.0",
 		"@internationalized/date": "^3.8.2",
 		"@lucide/svelte": "^0.525.0",
-		"@playwright/test": "^1.54.1",
 		"@sveltejs/adapter-static": "^3.0.8",
 		"@sveltejs/kit": "^2.26.0",
 		"@sveltejs/vite-plugin-svelte": "^6.1.0",