Add rewind after interruptions setting

[mpgirro]

This PR adds an optional "Rewind after interruptions" setting: when playback resumes after an audio interruption (phone call, alarm, Siri, CarPlay navigation prompt or another app taking over audio), Pocket Casts seeks back a configurable number of seconds so listeners don't lose context. This is especially useful in the car, where navigation prompts regularly interrupt playback. A matching PR with identical behavior is open for Android: Automattic/pocket-casts-android#5611.

Behavior

• New picker in Settings > General, directly below Intelligent Playback Resumption: Off, 5, 10, 15, 30, 60 seconds (default: 5 seconds once the feature flag is enabled).
• Rewind applies on both automatic resume (system .shouldResume) and manual resume after an interruption-caused pause.
• When Intelligent Playback Resumption would also rewind the same resume, the larger amount wins - the two never stack.
• Interruptions while already paused, route disconnections (headphone unplug) and ducking don't trigger it; the rewind clamps at 0:00.
• CarPlay inherits the behavior automatically via the shared playback engine.
• Behind the new interruptionRewind feature flag (default: debug builds only). The setting is device-local; adding it to named-settings sync would need a server-side key and is left as a possible follow-up for maintainers.

Implementation notes

• The interruption handler now records the frozen playback position and cancels the progress timer before storing the pause state - without this, the 1-second progress timer kept moving playedUpTo during the interruption and PlaybackCatchUpHelper's position guard rejected the adjustment on resume. This also benefits the existing Intelligent Playback Resumption after interruptions.
• PlaybackCatchUpHelper now computes the pause-length ladder and the interruption rewind separately and applies max() of the two.

To test

1. Run a debug build (flag interruptionRewind is enabled by default there) and start playing an episode.
2. Go to Settings > General > Rewind after interruptions and pick e.g. 30 seconds.
3. Trigger an interruption while playing: easiest is setting a timer/alarm that fires, or receiving a phone call.
4. When the alarm is dismissed / call ends, playback resumes automatically and starts ~30 seconds before the interruption point.
5. For a long interruption where iOS doesn't auto-resume: press play manually - the rewind still applies.
6. Set the setting to Off and verify resume happens exactly where playback stopped (for pauses shorter than 5 minutes).
7. Verify no stacking: with interruption rewind 60s, interrupt for >5 minutes, resume - playback rewinds 60s (not 70s). A manual pause of >5 minutes still gets the unchanged Intelligent Playback Resumption rewind (10s).
8. Verify a manual pause or unplugging headphones followed by resume does not trigger the interruption rewind.

Checklist

• I have considered if this change warrants user-facing release notes and have added them to CHANGELOG.md if necessary.
• I have considered adding unit tests for my changes.
• I have updated (or requested that someone edit) the Event Horizon schema to reflect any new or changed analytics. Maintainer action needed: this PR adds the settingsGeneralInterruptionRewindChanged event (value property = chosen seconds); I can't edit the schema repo as an external contributor.

[CLAassistant]

All committers have signed the CLA.

[dcamozzi]

Thanks for the suggestion and for taking the time to put together a PR. We've discussed it with the team and, at least for now, we don't plan to add a separate interruption rewind setting.

We appreciate the effort and will keep the feedback in mind as we continue to improve the listening experience.