chore: Semantic Versioning and a changelog from now on

Tags become three-part (v0.6.0), the header shows the full version and
pre-release tags no longer move :stable. CHANGELOG.md (Keep a Changelog)
starts with an Unreleased section; older versions will be added from the
history. The quantity field opens the number keypad on phones.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/vite.config.ts

@@ -2,10 +2,10 @@ import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react';
 import { readFileSync } from 'node:fs';
 
-// Shown in the header. Release builds get the git tag (APP_VERSION build argument, e.g. "v0.2");
-// other builds show the package version with a "-dev" suffix.
+// Shown in the header. Release builds get the git tag (APP_VERSION build argument, e.g. "v0.6.0");
+// other builds show the package version with a "-dev" suffix (Semantic Versioning, see CHANGELOG.md).
 const pkg = JSON.parse(readFileSync(new URL('./package.json', import.meta.url), 'utf8'));
-const appVersion = process.env.APP_VERSION || `v${pkg.version.replace(/\.0$/, '')}-dev`;
+const appVersion = process.env.APP_VERSION || `v${pkg.version}-dev`;
 
 export default defineConfig({
   plugins: [react()],