Fix random-mode toggle when altdomestick=1 is active

[thePunderWoman]

Summary

• When the alt button is held with altdomestick=1, enableAbsoluteStickMode() was overwriting fState even when the dome was in random mode. This caused toggleRandomMode() to see isRandomMode()==false and call enableRandomMode() instead of disableRandomMode(), so the toggle always turned random on and never off.
• Fixed by skipping abs-stick engage when isRandomMode() is true — keeps fState as kStateRandom while alt is held so the toggle check works correctly.
• Also added save/restore of fState across abs-stick engage/disengage as a general improvement (preserves any other active state, e.g. kStateGoToAngle).
• Updates example_config.txt to move the random-toggle action from lb=5 (long-press) to ab=5 (alt-press).

Test plan

• With altdomestick=1 and ab=5,9,0: toggle random mode on, then hold alt and press button 5 — random mode should turn off
• Toggle random mode off, hold alt and press button 5 — random mode should turn on
• With random mode active, holding alt should no longer briefly engage abs-stick mode
• With random mode off, holding alt should still engage abs-stick mode as normal
• pio test -e native passes (409/409)
• pio run succeeds

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