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

vitest.config.js

@@ -0,0 +1,17 @@
+import { defineConfig } from 'vitest/config'
+import vue from '@vitejs/plugin-vue'
+import path from 'path'
+
+export default defineConfig({
+  plugins: [vue()],
+  test: {
+    environment: 'jsdom',
+    globals: true,
+    include: ['src/**/*.test.js', 'src/**/*.spec.js']
+  },
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, 'src')
+    }
+  }
+})