fix: resolve stale state issues caused by missing React hook dependencies

[akashgoudsidduluri]

Summary

This PR resolves React Hook dependency warnings that could lead to stale closures and outdated state being used inside effects.

Changes

• Memoized callback functions with useCallback where required
• Updated useEffect dependency arrays
• Replaced stale state updates with functional state updates where appropriate
• Ensured effects and subscriptions remain synchronized with current state

Files Updated

• src/components/FocusTimer.tsx
• src/components/GroupPomodoro.tsx
• src/components/Room.tsx
• src/components/Whiteboard/Canvas.tsx
• src/pages/Dashboard.tsx
• src/pages/Leaderboard.tsx

Verification

• Ran npm run lint
• React Hook dependency warnings for the affected files are no longer reported
• No new ESLint errors introduced

Fixes #643

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[akashgoudsidduluri]

Hey @durdana3105 can you review this PR.

[durdana3105]

Hey @durdana3105 can you review this PR.

please resolve the merge conflicts

[akashgoudsidduluri]

Hey @durdana3105 i have resolved the conflicts, you can review it.