feat: add AI Project Tutor for interview preparation (closes #1733)

[Bhavy12-cell]

Closes #1733

Added an AI-powered Project Tutor to help users prepare for
technical interviews about their GitHub projects.

Features:

• Repository search bar — paste any GitHub repo URL
• AI-generated project analysis (summary, features, architecture)
• Interview questions at 3 difficulty levels (Easy, Medium, Advanced)
• AI chat interface to ask project-specific questions
• Uses Groq Llama3 API (same as existing AIMentorWidget)
• Fully responsive layout

Files added:

• src/app/project-tutor/page.tsx — page with auth guard
• src/app/api/project-tutor/route.ts — API endpoint
• src/components/ProjectTutorClient.tsx — client UI component

[vercel]

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[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — 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

[github-actions]

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