feat: Add "Print Profile / Export to PDF" action on Public Profile Page

[Doremon-tech-svg]

Closes #2604

What changed

• Added a Print Profile / Export to PDF button to the /u/[username] public profile header
• Button calls window.print() — zero external dependencies
• Button carries print:hidden so it never appears in the printed PDF
• Added @media print CSS rules in globals.css to:
  • Hide nav, footer, and all interactive elements
  • Remove card shadows for a clean paper layout
  • Prevent cards from splitting across pages
  • Set 1.5cm page margins

Acceptance criteria checklist

• No external dependencies — uses native browser window.print()
• Printed output is free from buttons and navigation
• Works in Chrome, Firefox, and Safari print dialogs

[github-actions]

GSSoC Label Checklist 🏷️

@Umbrella-io — please apply the appropriate labels before merging:

Difficulty (pick one):

• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

Quality (optional):

• quality:clean — ×1.2 multiplier
• quality:exceptional — ×1.5 multiplier

Validation (required to score):

• gssoc:approved — counts for points
• gssoc:invalid / gssoc:spam / gssoc:ai-slop — does not score

Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus

[Priyanshu-byte-coder]

Thanks for the contribution! We are currently in a code cleanup sprint and not accepting new features. Please see the discussion for details: #2651

This PR will be revisited once the sprint ends. In the meantime, contributions to testing, refactoring, bug fixes, or documentation are welcome.