fix(showcase): Correct base path to match GitHub repo name

Changed base from '/phantom-guard/' to '/phantom_guard/' to match
the actual GitHub repository name, fixing 404 errors for assets.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: matte1782

showcase/vite.config.js

@@ -1,7 +1,7 @@
 import { defineConfig } from 'vite';
 
 export default defineConfig({
-  base: '/phantom-guard/',  // For GitHub Pages
+  base: '/phantom_guard/',  // For GitHub Pages (must match repo name)
   build: {
     outDir: 'dist',
     assetsDir: 'assets',