feat(home): Improve Continue Reading cover with 1-bit Atkinson dithering

- Add 1-bit BMP generation with Atkinson dithering for better quality thumbnails
- Replace noise dithering with error diffusion for smoother gradients
- Add fillPolygon() to GfxRenderer for proper bookmark ribbon shape
- Change bookmark from rect+triangle carve to pentagon polygon
- Fix bookmark inversion when Continue Reading card is selected
- Show selection state on first render (not just after navigation)
- Fix 1-bit BMP palette lookup in Bitmap::readRow()
- Add drawBitmap1Bit() optimized path for 1-bit BMPs
The 1-bit format eliminates gray passes on home screen for faster rendering
while Atkinson dithering maintains good image quality through error diffusion.

lib/JpegToBmpConverter/JpegToBmpConverter.h

@@ -5,13 +5,15 @@ class Print;
 class ZipFile;
 
 class JpegToBmpConverter {
-  // [COMMENTED OUT] static uint8_t grayscaleTo2Bit(uint8_t grayscale, int x, int y);
   static unsigned char jpegReadCallback(unsigned char* pBuf, unsigned char buf_size,
                                         unsigned char* pBytes_actually_read, void* pCallback_data);
-  static bool jpegFileToBmpStreamInternal(class FsFile& jpegFile, Print& bmpOut, int targetWidth, int targetHeight);
+  static bool jpegFileToBmpStreamInternal(class FsFile& jpegFile, Print& bmpOut, int targetWidth, int targetHeight,
+                                          bool oneBit);
 
  public:
   static bool jpegFileToBmpStream(FsFile& jpegFile, Print& bmpOut);
   // Convert with custom target size (for thumbnails)
   static bool jpegFileToBmpStreamWithSize(FsFile& jpegFile, Print& bmpOut, int targetMaxWidth, int targetMaxHeight);
+  // Convert to 1-bit BMP (black and white only, no grays) for fast home screen rendering
+  static bool jpegFileTo1BitBmpStreamWithSize(FsFile& jpegFile, Print& bmpOut, int targetMaxWidth, int targetMaxHeight);
 };