feat: Add PDF export for interview feedback (#315)

[Diwakar-odds]

Closes #315

Description

This PR introduces a feature allowing users to download their AI-generated interview feedback as a nicely formatted PDF report.

Implementation Details:

• Added html2pdf.js for client-side HTML to PDF generation without requiring a backend endpoint.
• Updated the InterviewPrep page to include a "Download PDF" button next to the "Interview Q & A" section.
• Designed an off-screen, print-friendly hidden section (#pdf-report) in the UI that cleanly formats the user's role, experience, date, and expands all questions and AI-generated answers sequentially. This layout ensures the PDF report displays all information seamlessly, bypassing the accordion style used in the browser interface.

ECSoC26 Label Request

Analysis: This PR introduces a substantial new front-end feature to the application, implementing client-side PDF generation, structuring a custom printable UI layout, and integrating it with the existing AI interview session data.
Request: Could you please add the ECSoC26 label, along with the Level 2 label (and potentially good-ui or good-pr if applicable), as this represents a solid feature implementation? Thank you!

[Diwakar-odds]

Hi maintainers, could you please review this PR? It implements the PDF export feature for interview feedback, structuring the front-end layout specifically for print generation using html2pdf.js. As this is a substantial new feature on the frontend, I believe this aligns with Level 2 (UI/Fixes/Features). Could you please assign the \ECSoC26\ and \Level 2\ labels (and potentially \good-ui) if you agree? Thank you!

[KaranUnique]

@Diwakar-odds The AGENTS.md and contribution-rules.md files appear to be unrelated to the PDF export feature, could you please remove these changes from this PR to keep it focused on the requested feature?

also remove the package files

[Diwakar-odds]

@KaranUnique Thanks for the feedback! I've removed those unrelated files (AGENTS.md, contribution-rules.md, and the package files) from the PR. It now solely contains the PDF export feature.