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

.gitignore

@@ -0,0 +1,69 @@
+# Maven
+target/
+!.mvn/wrapper/maven-wrapper.jar
+!.mvn/wrapper/maven-wrapper.properties
+.mvn
+*.jar
+!.pom.xml
+
+# IDE
+.idea
+*.iml
+*.iws
+.project
+.classpath
+.settings
+.vscode
+
+# Logs
+*.log
+logs
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Database
+*.db
+*.db-journal
+
+# Uploads
+uploads/*
+!uploads/.gitkeep
+
+# Environment
+.env
+*.env.local
+
+# Build outputs
+dist/
+dist_new/
+
+# Mavis
+.mavis/
+.mcp/
+
+# Opencode
+.opencode/
+
+# Dependencies
+node_modules/
+
+# Temp files
+tmp_*.cjs
+tmp_*.js
+backend-stderr.txt
+backend-stdout.txt
+spawn-config.json
+worker1.json
+team-plan.yaml
+test-args.json
+
+# Test
+test-results/
+test-uploads/
+
+# Other
+*.bak
+matrix-media-*.png
+maven-wrapper.zip