Add bio field and enhance smart assignment with bio matching

- Add bio field to User model for judge/mentor profile descriptions
- Add bio step to onboarding wizard (optional step with 500 char limit)
- Enhance smart assignment to match judge bio against project description
  - Uses keyword extraction and Jaccard-like similarity scoring
  - Only applies if judge has a bio (no penalty for empty bio)
  - Max 15 points for bio match on top of existing scoring
- Fix geographic distribution query to use round relation for programId
- Update score breakdown: tags (40), bio (15), workload (25), country (15)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

prisma/schema.prisma

@@ -199,7 +199,8 @@ model User {
   country        String?     // User's home country (for mentor matching)
   metadataJson  Json?        @db.JsonB
 
-  // Profile image
+  // Profile
+  bio                  String?    // User bio for matching with project descriptions
   profileImageKey      String?    // Storage key (e.g., "avatars/user123/1234567890.jpg")
   profileImageProvider String?    // Storage provider used: 's3' or 'local'