feat: show build SHA + timestamp in a small footer for deploy verification

Adds a BuildStamp component pinned to the bottom-right of every page
(desktop only, dim monospace text) so it's obvious at a glance which
build is currently running.

The git short SHA and an ISO build timestamp are injected at build time
via Vite's `define`, falling back to 'unknown' if git is not available.
ESLint config declares the two compile-time constants as readonly
globals so no per-file disable comments are needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

eslint.config.js

@@ -14,7 +14,11 @@ export default defineConfig([
       reactRefresh.configs.vite,
     ],
     languageOptions: {
-      globals: globals.browser,
+      globals: {
+        ...globals.browser,
+        __BUILD_SHA__: 'readonly',
+        __BUILD_TIME__: 'readonly',
+      },
       parserOptions: { ecmaFeatures: { jsx: true } },
     },
     rules: {

src/App.jsx

@@ -2,6 +2,7 @@ import { Routes, Route, Navigate, Link } from 'react-router-dom'
 import { BookOpen, CheckSquare, LayoutDashboard, Trophy, Settings, LogOut } from 'lucide-react'
 import { useApp } from './store/AppContext'
 import Mark from './components/ui/Mark'
+import BuildStamp from './components/ui/BuildStamp'
 import ChatLauncher from './components/chat/ChatLauncher'
 
 import Login from './pages/Login'
@@ -88,6 +89,7 @@ function App() {
   if (state.isLoading) return <div className="p-8 flex items-center justify-center min-h-screen">Loading application...</div>
 
   return (
+    <>
       <Routes>
         <Route path="/login" element={<Login />} />
         <Route path="/" element={<ProtectedRoute><Dashboard /></ProtectedRoute>} />
@@ -96,6 +98,8 @@ function App() {
         <Route path="/leaderboard" element={<ProtectedRoute><Leaderboard /></ProtectedRoute>} />
         <Route path="/admin/*" element={<ProtectedRoute requireAdmin={true}><Admin /></ProtectedRoute>} />
       </Routes>
+      <BuildStamp />
+    </>
   )
 }
 

src/components/ui/BuildStamp.jsx

@@ -0,0 +1,19 @@
+const sha = typeof __BUILD_SHA__ === 'string' ? __BUILD_SHA__ : 'dev';
+const time = typeof __BUILD_TIME__ === 'string' ? __BUILD_TIME__ : new Date().toISOString();
+
+const formatted = (() => {
+  const d = new Date(time);
+  if (Number.isNaN(d.getTime())) return time;
+  return d.toLocaleString('nl-NL', { dateStyle: 'short', timeStyle: 'short' });
+})();
+
+const BuildStamp = () => (
+  <div
+    className="hidden md:block fixed bottom-1 right-2 text-[10px] font-mono text-fg-muted/60 z-40 pointer-events-none select-none"
+    title={`Build ${sha} at ${time}`}
+  >
+    v{sha} · {formatted}
+  </div>
+);
+
+export default BuildStamp;

vite.config.js

@@ -1,9 +1,24 @@
 import { defineConfig } from 'vite'
+import { execSync } from 'node:child_process'
 import react from '@vitejs/plugin-react'
 import tailwindcss from '@tailwindcss/vite'
 
+function getBuildSha() {
+  try {
+    return execSync('git rev-parse --short HEAD', { stdio: ['ignore', 'pipe', 'ignore'] })
+      .toString()
+      .trim()
+  } catch {
+    return 'unknown'
+  }
+}
+
 // https://vite.dev/config/
 export default defineConfig({
+  define: {
+    __BUILD_SHA__: JSON.stringify(getBuildSha()),
+    __BUILD_TIME__: JSON.stringify(new Date().toISOString()),
+  },
   plugins: [react(), tailwindcss()],
   server: {
     proxy: {