feat: Add Copy-to-Clipboard button for AI responses

[kareena0229]

📌 Related Issue

Closes #406

---

🚀 What does this PR do?

This PR adds a copy-to-clipboard feature for assistant chat responses in the frontend chat interface.

✨ Features Added

• Added a copy button for assistant responses
• Implemented clipboard copy functionality using navigator.clipboard
• Added success feedback with a check icon after copying
• Added temporary "Copied!" tooltip feedback
• Improved overall chat usability and accessibility

---

🧩 Type of Change

• Bug fix
• New feature
• Refactor / code cleanup
• Documentation update
• UI / styling change
• CI / tooling / config change
• Tests

---

🧪 How was this tested?

• Ran the frontend locally using npm run dev
• Verified copy button functionality manually
• Confirmed copied text is stored in clipboard
• Checked success state and tooltip rendering
• Ran npm run lint successfully with no warnings/errors

[kareena0229]

Implemented the feature and opened a PR for review.

[param20h]

Merge Conflicts

[kareena0229]

Resolved merge conflicts and updated branch with latest dev changes.
Frontend build issue was fixed after conflict resolution.
Current remaining failures appear related to existing Playwright/E2E tests.

[param20h]

Checks are failing

[kareena0229]

Resolved the frontend TypeScript/build issues and verified locally with npm run build successfully.

Only the Playwright E2E check is still failing now, which appears unrelated to the copy-to-clipboard implementation.

[kareena0229]

@param20h
There is no label yet, Could you please add the appropriate GSSoC label/level when available? Thanks!

[kareena0229]

@param20h waiting for review.