OpenBeken Charts Driver - configurable and flexible measurement history on your device

✨ The OpenBeken firmware introduces a configurable and scriptable charts driver enabling visualization of multiple variables with multiple axes directly on supported devices without requiring Home Assistant. The driver supports platforms based on BK7231T, BK7231N, BK7231M, T34, BL2028N, XR809, W800, LN882H, BL602, and others. Users configure charts via commands such as chart_create, chart_setVar, chart_setAxis, and addRepeatingEvent to plot variables like temperature, humidity, voltage, and power. Initial issues included crashes due to missing null checks in chart_setVar and chart_setAxis before chart_create, heap corruption from uninitialized memory, and platform-specific bugs such as vsnprintf handling null pointers. These were addressed through patches adding null checks, memory zeroing, and input validation to prevent crashes on invalid indexes. The charts driver was integrated with a ring buffer for data storage, with ongoing improvements to reduce flickering by updating charts instead of recreating them, and repositioning the chart below the "state" div to avoid page scroll jumps. Users reported stable long-term operation on various devices, including W600 and BL602, with some platform-specific driver enablement required in obk_config.h and Makefiles. The Windows simulator supports testing charts, facilitating development. Suggestions for future enhancements include adding a DIFF function to compute differences between consecutive samples. The driver supports variable expansion (e.g., $voltage*0.1) if ENABLE_EXPAND_CONSTANT is enabled. Sample configurations and troubleshooting tips were shared, including manual command sequences to generate pseudo-random data for testing. The charts driver is now considered production-ready with ongoing refinements and cross-platform support.