Implement Time Tracking Integration

Description: Add Pomodoro-style time tracking to tasks
Acceptance Criteria:

New command: tasktrek start

Live timer display with elapsed time

Automatic time logging to tasks

Weekly time reports
Files Affected:

tasktrek

tasktrek-lib.sh

New time-tracking.sh module
Suggested Approach:
Background process for timers. Store time data in separate JSON file
Difficulty Level: ⭐️⭐️⭐️⭐️ (4/5)

Start by reading tasktrek and tasktrek-lib.sh to understand command dispatch and shared behavior, then review the proposed time-tracking.sh module boundary. The work is done when `tasktrek start ` shows a live elapsed timer, logs time automatically to the separate JSON file, and produces weekly time reports.

Written by the indexing model from the issue text.