Fix sync retry handling

[hxu]

Why: interrupted or retried sync tasks should not leave progress and queue state inconsistent.

Example:

Queued tasks: activities 1219, gpx 975, health 4228, performance 604
Planning complete.
Act: 50/1267 | GPX: 545/1847 | Health: 0/4228 | Perf: 0/604 | 14m 37s

After cancelling and restarting, GPX/progress appeared to reset even though prior work was incomplete.

Changes:

• Improve retry/failure handling around sync tasks.
• Add coverage for resumed activity and GPX task counts.
• Keep progress totals aligned with queued work during resume.