Modernise frontend: latest toolchain, strict TypeScript, ESLint + Prettier

.gitignore

@@ -13,6 +13,7 @@ dist-ssr
 *.local
 
 # Editor directories and files
+.claude
 .vscode/*
 !.vscode/extensions.json
 .idea

.prettierignore

@@ -0,0 +1,4 @@
+dist
+node_modules
+package-lock.json
+src/maps

.prettierrc.json

@@ -0,0 +1,5 @@
+{
+  "semi": true,
+  "singleQuote": true,
+  "printWidth": 100
+}

eslint.config.ts

@@ -0,0 +1,31 @@
+import pluginVue from 'eslint-plugin-vue'
+import { defineConfigWithVueTs, vueTsConfigs } from '@vue/eslint-config-typescript'
+import skipFormatting from '@vue/eslint-config-prettier/skip-formatting'
+
+export default defineConfigWithVueTs(
+  {
+    name: 'app/files-to-lint',
+    files: ['**/*.{ts,mts,tsx,vue}'],
+  },
+
+  {
+    name: 'app/files-to-ignore',
+    ignores: ['**/dist/**', '**/dist-ssr/**', '**/coverage/**'],
+  },
+
+  pluginVue.configs['flat/essential'],
+  vueTsConfigs.recommended,
+  skipFormatting,
+
+  {
+    name: 'app/local-rules',
+    rules: {
+      // App-internal screens/widgets use single-word names (bar, map, taps…); there's no
+      // custom-element/DOM-tag collision risk here, so the multi-word rule isn't useful.
+      'vue/multi-word-component-names': 'off',
+      // This codebase wraps chart.js and introspects slot vnode props / untyped EMF API JSON,
+      // where `any` is sometimes warranted. Keep it visible as a warning rather than blocking.
+      '@typescript-eslint/no-explicit-any': 'warn',
+    },
+  },
+)