roadmap(gui): evaluate Plotters bitmap charts for 7/30d history

[xodapi]

Source

User-provided architecture note:

For future desktop dashboards, Slint + Plotters can render labeled charts by generating a bitmap/RGB buffer in the background and passing it into Slint as an image update. This is useful for future 7/30 day history with axes, labels, and grid lines.

Decision

Roadmap only. Do not implement during Android APK smoke-test or Slint testing work.

What to do later

Evaluate Plotters bitmap chart rendering for full 7/30 day history views.

Acceptance Criteria

• Keep as future roadmap until Android smoke-test and Slint testing path are stable.
• Do not add Plotters dependency in this issue.
• When implemented later, avoid relying on Android upgrade_in_event_loop without considering upgrade_in_event_loop not always processed slint-ui/slint#5699.
• Prefer background bitmap generation plus event-loop-safe coalesced UI update.

Checks

Docs/research only unless a future issue explicitly expands scope.