fix: FilePreview fileType case + Tailwind v4 gradient transparent bug

- FilePreview.vue: add normalizedFileType computed to handle backend
  returning uppercase HTML/MD/PPTX (fixes preview/download buttons)
- FilePreview.vue: bg-gradient-to-r from-orange-500 -> bg-orange-500
  (Tailwind v4 gradient + CSS variable = transparent)
- ReportCard.vue: bg-gradient-to-r -> bg-orange-600 for selected state
- Add .opencode/, node_modules/, dist/ to .gitignore
- Initial git setup for publish project

src/main.js

@@ -0,0 +1,8 @@
+import { createApp } from 'vue'
+import App from './App.vue'
+import router from './router'
+import './styles/main.css'
+
+const app = createApp(App)
+app.use(router)
+app.mount('#app')