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.lock

@@ -1768,6 +1768,12 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "http-range"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "21dec9db110f5f872ed9699c3ecf50cf16f423502706ba5c72462e28d3157573"
+
 [[package]]
 name = "httparse"
 version = "1.10.1"
@@ -4075,6 +4081,7 @@ dependencies = [
  "gtk",
  "heck 0.5.0",
  "http",
+ "http-range",
  "jni",
  "libc",
  "log",