Closes #197

Backend - Implement Advanced Search with Filters, Pagination, and Full-Text Search

Description

This PR implements a comprehensive search system for the Web3 Student Lab backend with the following features:

• Full-text search across courses (title, description, instructor), students (name, email), and certificates
• Advanced filtering with multiple operators (eq, neq, gt, gte, lt, lte, in, contains, startsWith)
• Pagination support with both offset-based and cursor-based pagination
• Multi-field sorting with ascending/descending order
• Search result metadata including execution time and total results
• Database indexes for optimal search performance

Key Components Added:

1. Search Infrastructure (src/search/):

   • SearchService.ts - Base search service class
   • SearchQueryBuilder.ts - Dynamic query building for filters and search
   • SearchValidator.ts - Input validation and sanitization
   • PaginationHelper.ts - Pagination logic for both offset and cursor methods
   • FilterParser.ts - Advanced filter parsing from query strings

2. Entity-Specific Search Services:

   • CourseSearchService.ts - Search courses with title, description, instructor
   • StudentSearchService.ts - Search students by name and email
   • CertificateSearchService.ts - Search certificates with enriched student/course data

3. API Endpoints (src/routes/search/):

   • GET /api/search/courses - Search courses
   • GET /api/search/students - Search students
   • GET /api/search/certificates - Search certificates
   • GET /api/search/all - Global search across all entities

4. Database Optimizations:

   • Added indexes on searchable fields for performance
   • Updated Prisma schema with proper indexing

API Usage Examples:

# Search courses with filters and pagination
GET /api/search/courses?query=soroban&filter[credits][gte]=3&sort=title:asc&page=1&limit=10

# Cursor-based pagination for certificates
GET /api/search/certificates?cursor=eyJpZCI6MTAwfQ==&limit=20

# Global search
GET /api/search/all?query=blockchain

Response Format:

{
  "data": [...],
  "pagination": {
    "page": 1,
    "limit": 10,
    "total": 45,
    "hasMore": true
  },
  "metadata": {
    "query": "soroban",
    "filters": { "credits": { "gte": 3 } },
    "sortBy": "title:asc",
    "executionTime": "45ms",
    "totalResults": 45
  }
}

Reference Issues

Fixes #197 Backend - Implement Advanced Search with Filters, Pagination, and Full-Text Search

Type of Change

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes