Region-of-interest JPEG decoder for ESP32. Decodes any rectangular sub-region of a JPEG without loading the full image, streaming output row-by-row so no full-frame buffer is required. Designed for LCD display use cases — provide your display dimensions and a pan offset, and the component handles scale selection, ROI math, and clamping internally. Built on TJpgDec. Supports FILE*, flash blobs, and PSRAM buffers as input sources. Runs on ESP32 (FreeRTOS async) and desktop (synchronous, for host testing).