web: scaffold Vue 3 + Vite app (create-vue, lean options)

Verbatim output of 'npm create vue@latest web -- --ts --vitest
--eslint --prettier' so this commit shows exactly what the official
scaffold generates; our own changes come separately. Lean per the
agreed choices: no Router/Pinia until a second page or shared state
exists. node_modules is ignored via the scaffold's own web/.gitignore.

web/.vscode/extensions.json

@@ -0,0 +1,10 @@
+{
+  "recommendations": [
+    "Vue.volar",
+    "vitest.explorer",
+    "dbaeumer.vscode-eslint",
+    "EditorConfig.EditorConfig",
+    "oxc.oxc-vscode",
+    "esbenp.prettier-vscode"
+  ]
+}