feat: Add image upload functionality with drag & drop, clipboard paste, and file picker (#46)

- Add drag & drop support for images with visual feedback
- Implement clipboard paste for images (Ctrl+V/Cmd+V)
- Add image upload button in chat interface
- Support multiple formats: PNG, JPG, JPEG, GIF, WebP, SVG
- Max 5 images per message, 5MB per image
- Add image preview with remove functionality
- Display images in chat message bubbles

Technical implementation:
- Frontend: Add react-dropzone for drag & drop
- Frontend: Create ImageAttachment component for previews
- Backend: Add multer for file upload handling
- Backend: Create /api/projects/:projectName/upload-images endpoint
- Backend: Convert images to base64 and save to temp files
- Claude CLI: Pass image paths as arguments
- Add automatic cleanup of temporary files
- Fix JWT auth to use correct token name
- Fix UI overlap with proper padding adjustments
- Remove non-essential console.logs for production

Security:
- Validate file types and sizes
- Sanitize filenames
- User-specific temp directories
- Proper JWT authentication

Infrastructure:
- Add .tmp/ to .gitignore
- Create comprehensive CHANGELOG.md
- Update package.json with new dependencies

Co-authored-by: viper151 <simosmik@gmail.com>

.gitignore

@@ -90,6 +90,7 @@ jspm_packages/
 # Temporary folders
 tmp/
 temp/
+.tmp/
 
 # Vite
 .vite/