feat: display app version in footer

Inject version from package.json at build time via Vite's define and
show it in the layout footer.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

vite.config.ts

@@ -1,9 +1,15 @@
+import { readFileSync } from 'node:fs';
 import { sveltekit } from '@sveltejs/kit/vite';
 import { SvelteKitPWA } from '@vite-pwa/sveltekit';
 import tailwindcss from '@tailwindcss/vite';
 import { defineConfig } from 'vite';
 
+const pkg = JSON.parse(readFileSync('package.json', 'utf-8'));
+
 export default defineConfig({
+	define: {
+		__APP_VERSION__: JSON.stringify(pkg.version)
+	},
 	plugins: [
 		tailwindcss(),
 		sveltekit(),