feat(currency-hub): add pagination, filtering, and search support with Swagger docs

[mdauwal]

🚀 Currency Hub: Paginated, Searchable Currency Data API

Summary

This PR enhances the currency-hub module with:

• ✅ Pagination (page, limit)
• 🔍 Search by base/target currency or provider
• 🔄 Advanced filtering via QueryCurrencyHubDto
• 📄 Swagger documentation via @ApiQuery, @ApiOperation

What's Included

• QueryCurrencyHubDto — updated with page, limit, and search
• currency-hub.service.ts — updated findAll method with full logic
• currency-hub.controller.ts — updated with Swagger decorators and updated endpoint

How to Test

• Visit GET /currency-hub
• Try queries like:
  • ?page=1&limit=10
  • ?search=USD
  • ?baseCurrencyCode=USD&targetCurrencyCode=NGN

Closes

Closes #56

[portableDD]

Where is this function, what happened to the?, please return them?

[mdauwal]

This update merges enhanced filtering, pagination, and search capabilities into the existing CurrencyHub service logic while retaining all operational methods such as:

• findOne
• convertCurrency
• getBestProvider
• getHistoricalTrend

✅ Preserves all existing business logic
✅ Adds paginated findAll with filters and search
✅ Maintains structure and testability for upcoming versioning