Fix: display validation errors correctly for both email and password when invalid

[ToseebNadaf]

PR Fixes:

• Added Zod validation for email and password.
• Replaced useRef with useState for better state management.
• Memoized handleEmailChange with useCallback to prevent unnecessary re-renders.
• Implemented client-side form validation before sign-in attempt.
• Mapped error responses to display meaningful error messages.

Resolves #1714

Checklist before requesting a review

• [✅] I have performed a self-review of my code
• [✅] I assure there is no similar/duplicate pull request regarding same issue

Before -->

https://github.com/user-attachments/assets/75d20992-6d3f-48bf-ad51-714ea14bcafd

After -->

https://github.com/user-attachments/assets/0d7147a9-18ef-4647-bc55-cf0258280101

[ToseebNadaf]

@devsargam suggest any changes if needed