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/App.vue

@@ -0,0 +1,16 @@
+<template>
+  <div class="min-h-screen bg-gradient-to-br from-orange-100 via-orange-200 to-amber-100">
+    <router-view />
+  </div>
+</template>
+
+<script setup>
+</script>
+
+<style>
+html, body {
+  margin: 0;
+  padding: 0;
+  background: transparent;
+}
+</style>