feat(about): two-column build info, show git commit hash

- Build Info grid now uses 2-column layout (Version|License, Platform|Build)
- Build field shows date + short commit hash (6 chars) injected at
  build time via VITE_BUILD_COMMIT

vite.config.js

@@ -1,6 +1,7 @@
 // @ts-nocheck - Node.js globals used in vite config
 import { defineConfig } from "vite";
 import { sveltekit } from "@sveltejs/kit/vite";
+import { execSync } from "child_process";
 
 const host = process.env.TAURI_DEV_HOST;
 
@@ -11,6 +12,9 @@ export default defineConfig(async () => ({
     'import.meta.env.VITE_BUILD_DATE': JSON.stringify(
       new Date().toISOString().split('T')[0]
     ),
+    'import.meta.env.VITE_BUILD_COMMIT': JSON.stringify(
+      (() => { try { return execSync('git rev-parse --short=6 HEAD').toString().trim(); } catch { return ''; } })()
+    ),
     // Immersive rendering feature flag (WebGL2-based effects)
     // Set QBZ_IMMERSIVE=false to compile out immersive rendering
     'import.meta.env.VITE_IMMERSIVE_ENABLED': JSON.stringify(