Add Multitouch rollover support for the gamepad buttons

[SerSaumy]

What this does

Replaces the per-button clickable gesture detectors on the D-pad, face buttons,
shoulder buttons, and menu buttons with a shared MultiTouchController that
hit-tests every active pointer against every button's bounds. This adds two
related behaviors:

• Multi-touch, up to 4 simultaneous fingers (MAX_TRACKED_TOUCH_POINTS in
  the new TouchZoneController.kt) — previously each button's gesture detector
  only knew about its own pointer, with no shared limit or coordination across
  the cluster.
• Rollover / slide-to-switch: press a button, then without lifting your
  finger, drag it onto a different button — the first releases and the second
  presses automatically. No need to lift and re-tap to switch buttons mid-gesture.

Analog sticks (AnalogStick.kt) and triggers (Trigger.kt) are unchanged
on purpose — they're continuous drag controls, not discrete buttons, so
rollover doesn't apply to them the same way.

Why

Each button previously owned its own MutableInteractionSource + clickable,
so no button's gesture detector could know a finger had slid over from a
neighboring button, and there was no single place to reason about "how many
fingers is this cluster tracking." Rollover requires looking at all buttons'
bounds and all active pointers together, so the touch handling moved to one
shared controller instead.

Changes

• New: ui/composables/TouchZoneController.kt — MultiTouchController
  (zone registration, pointer-to-zone tracking, hit-testing, press/release
  callbacks), Modifier.multiTouchDispatcher (manual low-level pointer
  tracking via awaitPointerEventScope), Modifier.touchZone (per-button
  registration), plus LocalMultiTouchController / LocalTouchContainerCoordinates.
• Modified: ui/composables/Gamepad.kt — wires the shared controller and
  container coordinates into DrawGamepad via CompositionLocalProvider,
  releases all buttons on teardown so nothing gets stuck "pressed."
• Modified: ui/composables/FaceButtons.kt, Dpad.kt, CentralButtons.kt
  — swapped Button/OutlinedButton/OutlinedIconButton + clickable for
  Surface + Modifier.touchZone, with an animated background tint on press
  (replacing the ripple lost by moving off clickable).

Testing

Built and tested on-device (not just emulator, since emulators generally only
simulate 1-2 touch points). Verified:

• Multiple fingers on different buttons register and stay independent
• Holding a button and sliding to another correctly releases/presses across
  the transition
• Holding 4 buttons at once works; a 5th simultaneous touch is ignored rather
  than stealing a tracking slot
• No buttons get stuck "pressed" after rotating the screen or navigating away
  mid-touch

Notes

• MAX_TRACKED_TOUCH_POINTS is a single constant if this limit should be
  raised/lowered later.
• Happy to split this into smaller commits or adjust the zone-id scheme
  (face_A, dpad_UP, shoulder_LEFT, etc.) if you'd prefer a different
  convention.

[sonarqubecloud]

Quality Gate failed

Failed conditions
13.4% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud