v4.30.0 — Price scrolling and reset view

Added

• Experimental priceScroll on LiveChart pans the price window with a vertical
  drag on the plot, which together with timeScroll gives free X/Y panning. By
  default (activation: "afterScale") it engages only once the range was
  manually changed by a price-axis drag, a pinch or an earlier price pan, so an
  untouched chart still lets a parent ScrollView scroll; "always" claims every
  vertical drag. The pan writes viewport.range (the app's shared value when
  supplied, otherwise private state), and the engine keeps a gesture-written
  range active while following live, clamped to nonNegative, maxValue and
  minRange. Travel stops maxOvershoot visible spans past the fitted range.
  Price-axis drags scale a panned window in place, a double tap on the axis
  clears it, and so does a snapKey or mode change.

• Experimental resetButton on LiveChart floats a reset-view control inside
  the plot ("bottom-center" or "bottom-right") while the view differs from
  the fitted live view: scrolled back, pinched, scaled or price-panned, with
  showFor choosing which states count. The built-in button draws a glyph in
  palette colors; renderResetButton supplies a custom visual while the chart
  keeps placement, visibility, fade and the tap. onResetView fires after a
  reset.

• LiveChartHandle.resetView() on both charts returns to the fitted live view:
  resetZoom() plus yRangeScale back to 1 and, on LiveChart, a
  gesture-written price range cleared, using the returnToLive glide.

• The Time scroll demo adds Price scroll (Off / After scale / Always) and
  Reset view settings; a dedicated Reset view demo links directly to its
  matching guide, and the Fomo perps showcase shows the reset button.

Fixed

• Price panning relinquishes ownership on app-written price bounds or a
  replacement viewport.range, preserving those bounds during resets and
  framing changes.
• onResetView now fires after reset overrides are applied on the UI thread
  for imperative resets and accessibility activation, matching button taps.
• The built-in reset button handles Android TalkBack activation. Custom-button
  documentation includes the Android accessibility action alongside the iOS tap.