feat(sync): show last completion status

[TimeToBuildBob]

Problem

#247 reports that sync runs silently: users cannot tell whether it succeeded, failed, or when it last completed. A failed SAF mirror was also logged as non-fatal, so the app could report native sync success while the user-selected directory stayed unchanged.

Fix

• Persist the timestamp and outcome of each full sync attempt.
• Show Last sync: never, Last sync succeeded at …, or Last sync failed at … in Sync Settings.
• Treat a failed configured-directory mirror as a failed worker sync instead of silently reporting success.
• Keep the status compact and avoid persisting native error details, which can include filesystem paths.

This addresses the feedback/status portion of #247. The 401 root cause, document picker, and unknown Activity route are already merged via #249, #248, and #250. Category-import persistence remains separate.

Testing

JAVA_HOME=/opt/android-studio/jbr ANDROID_HOME=/home/bob/Android/Sdk \
  ./gradlew :mobile:testDebugUnitTest --no-daemon

Passed (full JVM unit-test suite).

[greptile-apps]

Greptile Summary

This PR persists the outcome and completion time of full sync attempts and displays that status in Sync Settings.

• Full-sync callers now wait for configured SAF mirroring and treat inaccessible, interrupted, or incomplete mirrors as failures.
• Sync status changes are persisted without native error details and broadcast to refresh the visible settings screen.
• Unit tests cover formatting for never-run, successful, and failed states.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains; the previously reported mirror-failure, stale-status, and partial-mirror cancellation paths are addressed at the current head.

Important Files Changed

Filename	Overview
mobile/src/main/java/net/activitywatch/android/AWPreferences.kt	Persists compact sync completion metadata and broadcasts status changes after updating preferences.
mobile/src/main/java/net/activitywatch/android/SyncInterface.kt	Records full-sync outcomes only after native synchronization and configured SAF mirroring complete.
mobile/src/main/java/net/activitywatch/android/SyncSettingsActivity.kt	Formats the saved status and refreshes it through lifecycle reconciliation and a package-scoped receiver.
mobile/src/main/res/layout/activity_sync_settings.xml	Adds the compact last-sync status row to Sync Settings.
mobile/src/test/java/net/activitywatch/android/SyncSettingsActivityTest.kt	Covers status text for no prior attempt and successful or failed completion.

Sequence Diagram

sequenceDiagram
    participant Trigger as Scheduler / Worker
    participant Sync as SyncInterface
    participant SAF as Configured SAF directory
    participant Prefs as AWPreferences
    participant UI as Sync Settings

    Trigger->>Sync: Start full sync
    Sync->>Sync: Run native synchronization
    alt Native sync succeeds
        Sync->>SAF: Mirror sync files
        SAF-->>Sync: Complete or throw
    end
    Sync->>Prefs: Persist completion time and outcome
    Prefs-->>UI: Send package-scoped status broadcast
    UI->>Prefs: Read latest status
    UI->>UI: Refresh status row

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_{Reviews (3): Last reviewed commit: "fix(sync): fail incomplete SAF mirrors" | Re-trigger Greptile}

[TimeToBuildBob]

@greptileai review

[TimeToBuildBob]

@greptileai review

[TimeToBuildBob]

CI-green and mergeable (Greptile 5/5) — waiting only on a maintainer click.

This PR is ready to merge, but the bot has pull-only access to this repo and can't self-merge. The last Greptile P1 thread (cancellation during SAF mirroring) was already fixed in 67343c2 and is now resolved.