Add skip-next alarm with undo and feature-aware What's New

[t-regbs]

Summary

Add Skip next and Undo for weekly alarms and multi-day non-repeating alarms. Skipping removes only the next occurrence, preserves the remaining schedule and snooze, and survives recovery. Single-day one-time alarms do not offer Skip.

• Show the skipped date and next valid occurrence with localized copy and shared alarm-card formatting.
• Preserve future and recently due snoozes during Skip/Undo. Reject obsolete deliveries and validate Android playback against the saved active occurrence so deleted, disabled, completed, or snoozed alarms cannot restart from a delayed service request.
• Add an interactive skip-alarm announcement. Track What's New acknowledgement per feature so users who skip releases see all unseen features. Settings replays their latest update group, with arrow/bar navigation separated from feature actions.
• Migrate the old announcement preference by preserving its known acknowledgement; previously forgotten history cannot be reconstructed.

Validation

• Final cancellation pass: 351 Android host tests and 121 core iOS simulator tests passed (472 total).
• Shared iOS simulator suite: 152 tests passed in the preceding review pass.
• Android debug build and git diff --check passed.
• Earlier Android emulator checks covered Skip/Undo presentation, announcement navigation, migration, restart persistence, and Settings replay.
• Physical-device alarm delivery was not exercised in the final cancellation pass.

Regression coverage includes weekly and finite schedules, snooze delivery boundaries, deleted/obsolete deliveries, queued playback, recovery, sequential updates, and skipped releases. See docs/skip-next-alarm-review.md for review details.