[Frontend] Add PDF certificate generation and download for earned credentials

[Penielka]

Description

Users who earn credentials should be able to download a professionally formatted PDF certificate. The certificate should include: credential title, recipient name (wallet address), issuer name, issue date, verification hash, and a QR code linking to on-chain verification.

Definition of Done

• PDF generation library integrated (e.g., @react-pdf/renderer or jspdf)
• Certificate template with AetherMint branding
• Dynamic fields: credential name, recipient, issuer, date, hash
• QR code with verification URL embedded in certificate
• Download button on credential detail page
• PDF renders correctly in browser preview and download
• Certificate is print-ready (300 DPI, proper margins)
• Responsive: works on mobile and desktop

Acceptance Criteria

1. Click "Download Certificate" on a credential detail page
2. PDF downloads with correct metadata and formatting
3. QR code scans to correct verification URL
4. Certificate looks professional with branding, borders, and proper typography

Files to Modify

• frontend/package.json — add @react-pdf/renderer or jspdf + qrcode
• New file: frontend/src/components/Credentials/CertificatePDF.tsx — PDF template
• New file: frontend/src/utils/certificateGenerator.ts — generation logic
• frontend/src/components/CredentialList.tsx — add download button
• frontend/src/components/CredentialBridge/index.tsx — add download button

[Peolite001]

i would love to work on this issue

[gloskull]

Hello, I have 4 years of experience delivering solutions for projects like this, covering backend, frontend, and smart contract development. After carefully reviewing your requirements, I have a clear understanding of the task and am confident in my ability to deliver a clean, efficient, and thoroughly tested solution on time. I prioritize code quality, maintainability, and industry best practices throughout the development process.
My PR will be submitted in under 10hours.

[clintjeff2]

Hello, I have 6 years of experience working on tasks like this and handling similar challenges across backend, frontend, and smart-contract development. I have carefully read and fully understood the task requirements, and I am confident I can deliver a clean, efficient, and well-tested solution promptly. I always ensure high-quality implementation, maintainability, and adherence to best practices.

Pull request in 5 hours.