feat: add build version display to all views

Add build version indicator to verify code updates:

1. Create BuildVersion.vue component:
   - Displays in top-right corner (fixed position)
   - Format: YYYYMMDDHHMMSS-gitHash
   - Example: 20260725133504-39ce37e

2. Update vite.config.ts:
   - Inject __BUILD_VERSION__ global variable
   - Generated from build time + git commit hash

3. Add to App.vue:
   - Shown on all views automatically
   - Z-index: 9999 (always visible)

4. Add vite-env.d.ts:
   - TypeScript declarations for __BUILD_VERSION__

Purpose:
- User can verify if browser loaded latest code
- Easy to confirm updates are deployed
- No need to check source code

Location: Top-right corner, fixed position
Format: Monospace font, small text, subtle styling

vite.config.ts

@@ -1,9 +1,17 @@
 import { defineConfig } from 'vite'
 import vue from '@vitejs/plugin-vue'
 import { resolve } from 'path'
+import { execSync } from 'child_process'
+
+const gitHash = execSync('git log --format="%h" -1', { encoding: 'utf-8' }).trim()
+const buildTime = new Date().toISOString().slice(0, 19).replace(/[-:T]/g, '')
+const buildVersion = `${buildTime}-${gitHash}`
 
 export default defineConfig({
   plugins: [vue()],
+  define: {
+    __BUILD_VERSION__: JSON.stringify(buildVersion)
+  },
   resolve: {
     alias: {
       '@': resolve(__dirname, 'src')