fix: Increase PNGdec buffer size to support wide images (#995)

## Summary

* Increased `PNG_MAX_BUFFERED_PIXELS` from 6402 to 16416 in
`platformio.ini` to support up to 2048px wide RGBA images
* adds a check to abort decoding and log an error if the required PNG
scanline buffer exceeds the configured `PNG_MAX_BUFFERED_PIXELS`,
preventing possible buffer overruns.
* fixes
https://github.com/crosspoint-reader/crosspoint-reader/issues/993

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platformio.ini

@@ -31,9 +31,9 @@ build_flags =
   -std=gnu++2a
 # Enable UTF-8 long file names in SdFat
   -DUSE_UTF8_LONG_NAMES=1
-# Increase PNG scanline buffer to support up to 800px wide images
+# Increase PNG scanline buffer to support up to 2048px wide images
 # Default is (320*4+1)*2=2562, we need more for larger images
-  -DPNG_MAX_BUFFERED_PIXELS=6402
+  -DPNG_MAX_BUFFERED_PIXELS=16416
 
 build_unflags =
   -std=gnu++11