fix: Task State Inconsistency

[enochpromo]

MR Summary: Fix task persistence race conditions after refresh

• Improved state updates and persistence to prevent lost/duplicated tasks after page refresh.
• Replaced stale-closure patterns with functional state updates in useTasks.
• Centralized persistence with a hydration-guarded effect; added debounce for write coalescing.
• Added immediate saves on critical operations (add/toggle/delete) to ensure durability.
• Stopped default writes during initial load to avoid write-before-read races.
• Added robust tests simulating remount/refresh; mocked delays and debounce to stabilize.
  Key changes:
• src/hooks/useTasks.ts
  • Functional setTasks, hydratedRef to gate writes.
  • Debounced save effect using APP_CONFIG.AUTO_SAVE_DELAY.
  • Immediate taskService.saveTasks(updatedTasks) on add/toggle/delete when hydrated.
• src/services/taskService.ts
  • Removed save during loadTasks when defaults are used.
• src/hooks/__tests__/useTasks.test.tsx
  • Added tests for add without refresh, add with remount, toggle+add with remount.
  • Mocked delays and disabled debounce for deterministic execution.
    Outcome:
• Eliminates out-of-order localStorage writes and stale overwrites.
• Tasks reliably persist across rapid actions and page reloads.
• All tests passing.