feat: add image preview with drag-and-drop support

- Add ImagePreview component for displaying embedded image thumbnails
- Enable drag-and-drop functionality for images in FloatingPromptInput
- Configure Tauri asset protocol to properly serve local image files
- Support image mentions via @path syntax in prompts
- Add visual feedback for drag hover states
- Implement full-size image preview dialog with navigation
- Handle duplicate images and limit preview to 10 thumbnails

src-tauri/Cargo.toml

@@ -18,7 +18,7 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 tauri-build = { version = "2", features = [] }
 
 [dependencies]
-tauri = { version = "2", features = [] }
+tauri = { version = "2", features = ["protocol-asset"] }
 tauri-plugin-opener = "2"
 tauri-plugin-shell = "2"
 tauri-plugin-dialog = "2.0.3"