feat(build): add update-version.js to auto-increment patch on every build

Script runs before vite build via package.json "build" script.
Reads/writes APP_VERSION in frontend/constants.ts (now at V1.0.3).

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

frontend/constants.ts

@@ -1 +1 @@
-export const APP_VERSION = 'V1.0.2';
+export const APP_VERSION = 'V1.0.3';

frontend/package.json

@@ -5,7 +5,7 @@
   "type": "module",
   "scripts": {
     "dev": "vite",
-    "build": "vite build",
+    "build": "node ../update-version.js && vite build",
     "preview": "vite preview"
   },
   "dependencies": {

update-version.js

@@ -0,0 +1,24 @@
+#!/usr/bin/env node
+// Increments the patch number in frontend/constants.ts before every build.
+// Called via: node ../update-version.js (from inside frontend/)
+const fs = require('fs');
+const path = require('path');
+
+const constantsPath = path.join(__dirname, 'frontend', 'constants.ts');
+const content = fs.readFileSync(constantsPath, 'utf8');
+
+const match = content.match(/APP_VERSION\s*=\s*['"]V(\d+)\.(\d+)\.(\d+)['"]/);
+if (!match) {
+    console.error('[update-version] Could not parse APP_VERSION in constants.ts');
+    process.exit(1);
+}
+
+const [, major, minor, patch] = match;
+const next = `V${major}.${minor}.${parseInt(patch, 10) + 1}`;
+const updated = content.replace(
+    /APP_VERSION\s*=\s*['"]V\d+\.\d+\.\d+['"]/,
+    `APP_VERSION = '${next}'`
+);
+
+fs.writeFileSync(constantsPath, updated, 'utf8');
+console.log(`[update-version] ${match[0].match(/V\d+\.\d+\.\d+/)[0]} → ${next}`);