fix: recover from stale capture locks

[yahorbarkouski]

Summary

• replace the scheduler's promise lock with an expiring timed lease so scheduled captures skip safely and manual captures only wait up to the lease timeout
• add matching stale in-flight recovery to activity-window candidate capture so window finalization cannot block forever behind a hung screenshot
• add regression coverage for stale manual captures, scheduled retry after timeout, and activity-window recovery

Testing

• npm test -- electron/main/features/scheduler/tests/SchedulerService.test.ts electron/main/features/activityWindow/tests/ActivityWindowService.test.ts
• npm run typecheck
• npx biome check electron/main/infra/async/timedLease.ts electron/main/features/scheduler/SchedulerService.ts electron/main/features/activityWindow/ActivityWindowService.ts electron/main/features/scheduler/tests/SchedulerService.test.ts electron/main/features/activityWindow/tests/ActivityWindowService.test.ts

Closes #5

[github-actions]

🎉 This PR is included in version 1.30.0 🎉

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