feat: Add RGBW LED support and hardware communication protocol

- Add RGBW LED type support alongside existing RGB LEDs
- Implement 4-channel RGBW data transmission (R,G,B,W bytes)
- Add RGBW visual preview with half-color, half-white gradient display
- Fix RGB color calibration bug in publisher (was not being applied)
- Create comprehensive hardware communication protocol documentation
- Support mixed RGB/RGBW LED strips on same display
- Add W channel color temperature adjustment in white balance page
- Hardware acts as simple UDP-to-WS2812 bridge without type distinction

src-tauri/src/led_color.rs

@@ -43,6 +43,10 @@ impl LedColor {
     pub fn as_bytes (&self) -> [u8; 3] {
         self.0
     }
+
+    pub fn as_bytes_rgbw(&self, w: u8) -> [u8; 4] {
+        [self.0[0], self.0[1], self.0[2], w]
+    }
 }
 
 impl Serialize for LedColor {