build: update to node 22 and pnpm (#3616)

This commit brings the project to support node 22 which became LTS and
fixes broken builds with typescript 5.7+ until vue-tsc is updated and
replaces npm with pnpm.

- Update tsconfig for node 22
- Pin typescript to 5.6.x to not break vue-tsc
- Replace npm with pnpm (corepack recommended)
- Update Makefile and main workflow for pnpm
- Migrate to eslint 9 flat config
- Fix broken imports
- Exclude non-TS vue files for vue-tsc

frontend/tsconfig.node.json

@@ -0,0 +1,18 @@
+{
+  "extends": "@tsconfig/node22/tsconfig.json",
+  "include": [
+    "vite.config.*",
+    "vitest.config.*",
+    "cypress.config.*",
+    "nightwatch.conf.*",
+    "playwright.config.*"
+  ],
+  "compilerOptions": {
+    "composite": true,
+    "noEmit": true,
+    "tsBuildInfoFile": "./node_modules/.tmp/tsconfig.node.tsbuildinfo",
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "types": ["node"]
+  }
+}