feat(mobile): native iOS segmented control for My Issues scope switcher (MUL-3402)

[voska]

What does this PR do?

Replaces the custom outline-pill row in the My Issues scope switcher (Assigned / Created / Agents) with the native iOS UISegmentedControl (@react-native-segmented-control, already a dependency).

This brings the authentic iOS connected-segment look, the native sliding-selection animation, and the system selection haptic on change — none of which the hand-rolled pills had.

Related Issue

N/A — native-feel polish; no tracking issue.

Closes #

Type of Change

• New feature (non-breaking change that adds functionality)
• Refactor / code improvement (no behavior change)

Changes Made

• app/(app)/[workspace]/(tabs)/my-issues.tsx — ScopeToolbar now renders <SegmentedControl> instead of a row of outline <Button> pills; appearance follows the app color scheme for dark mode. Net −3 lines (the native control replaces hand-rolled markup).

How to Test

1. Open My Issues.
2. The Assigned / Created / Agents switcher renders as a native iOS segmented control.
3. Tapping a segment slides the selection (and fires a selection haptic on device).

Checklist

• If this change affects the UI, I have included before/after screenshots
• pnpm typecheck passes; verified manually in the iOS Simulator
• No automated test — native control rendering

AI Disclosure

AI tool used: Claude Code

Prompt / approach: Identified the hand-rolled pills as a non-native pattern during a native-feel review, then swapped to the already-installed native UISegmentedControl. Verified before/after + the slide animation in the iOS Simulator.

Screenshots

Before (custom pills) / after (native segmented control):

Sliding-selection clip: native-segmented-slide.mp4

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