Fix AxisChange/Invalidate call order in ZedGraph controls

[Copilot]

zg.Invalidate() was being called before zg.AxisChange() in multiple places, meaning the control redraws with a stale axis scale. This was most visible when unchecking a curve in the telemetry log graph — the remaining curves' Y-axis scale would not update.

The correct order is always AxisChange() then Invalidate().

Changes

• Log/MavlinkLog.cs — 3 locations fixed:
  • treeView1_NodeMouseClick: added missing AxisChange() before Invalidate() (only Invalidate() was present)
  • Two locations in chk_box_CheckedChanged: swapped reversed call order
• Controls/fftui.cs — 5 locations fixed: all had Invalidate() before AxisChange()

// Before (wrong — redraws before axis scale is recalculated)
zg1.Invalidate();
zg1.AxisChange();

// After (correct)
zg1.AxisChange();
zg1.Invalidate();