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.tsc.json

@@ -0,0 +1,14 @@
+{
+  "extends": "./tsconfig.app.json",
+  // vue-tsc wont shut up about error TS9005
+  // in non-TS vue files so exclude them
+  "exclude": [
+    "src/components/Shell.vue",
+    "src/components/prompts/Copy.vue",
+    "src/components/prompts/Delete.vue",
+    "src/components/prompts/FileList.vue",
+    "src/components/prompts/Rename.vue",
+    "src/components/prompts/Share.vue",
+    "src/components/prompts/UploadFiles.vue"
+  ]
+}