refactor: convert SPA to multi-page architecture

- Add scene_onboarding.html, scene_dashboard.html, scene_settings.html
- Add onboarding.js, dashboard.js, settings.js scripts
- Update vite.config.js for multi-page build
- Navigation via window.location.href between pages
- Bottom nav bar on dashboard only

vite.config.js

@@ -0,0 +1,26 @@
+import { defineConfig } from 'vite'
+import { resolve } from 'path'
+
+export default defineConfig({
+  root: 'src',
+  build: {
+    outDir: '../dist',
+    emptyOutDir: true,
+    rollupOptions: {
+      input: {
+        main: resolve(__dirname, 'src/index.html'),
+        onboarding: resolve(__dirname, 'src/pages/scene_onboarding.html'),
+        dashboard: resolve(__dirname, 'src/pages/scene_dashboard.html'),
+        swipe: resolve(__dirname, 'src/pages/scene_swipe.html'),
+        settings: resolve(__dirname, 'src/pages/scene_settings.html'),
+        'ai-classification': resolve(__dirname, 'src/pages/scene_ai_classification.html'),
+        gamification: resolve(__dirname, 'src/pages/scene_gamification.html'),
+        visualization: resolve(__dirname, 'src/pages/scene_visualization.html'),
+      }
+    }
+  },
+  server: {
+    port: 5173,
+    strictPort: true
+  }
+})