[Jdreioe]

Summary

Completes #120's selection feedback. Screens and the Typing Screen now share one Android timer; the compact Phrase row also shows feedback. Selection uses static inset black/white rings, leaving focus and dwell feedback visible. Desktop adds the same feedback and a persisted duration under Settings > Access, with 0 disabling it. iOS gets the ring and timer corrections.

select target -> move highlight, replace expiry timer
change duration -> update expiry, clear when disabled
new selection -> old expiry cannot clear it

Closes #120. Stacked on the #225 cleanup; merge that first.

Evidence

• Before: Android emulator tests failed because disabling feedback retained the active overlay and the expected contrasting inner ring was absent.
  After: both UI tests pass, including selection alongside focus. Shared timing tests pass.
• Desktop: 51 Rust tests pass, including stale expiry and disabled feedback. Kotlin/Native binding tests pass, including duration clamping and persistence across reopen. Rust formatting passes.
• iOS was source-reviewed only. This Linux host has no Xcode or iOS Simulator; build/device verification remains necessary. Desktop was tested on Linux, not Windows or macOS.

Merge Danger

Door: two-way

Blast Radius: feedback

No animation or schema migration. Desktop's JSON adds a defaulted duration field. iOS compilation and visual checks are the remaining validation limit.