feat: liquidity aggregator module with routing, pricing, monitoring, and arbitrage analysis

[uadamu00005-netizen]

Closes #46

Summary

This PR introduces a new Liquidity Aggregator module to support pool registration, pricing, route analysis, execution simulation, and arbitrage detection across the trading platform. It establishes the core infrastructure needed for liquidity-aware trade routing and market monitoring.

Related Issues

Part of the liquidity and routing feature set for the trading platform.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that changes existing behaviour)
• Documentation only
• Refactor / chore (no functional change)

Changes

• Added a new LiquidityAggregatorModule and registered it in the app bootstrap
• Implemented pool registry and liquidity data model for pool tracking
• Added price oracle, route graph, and pricing services
• Added multi-route splitting and price impact estimation logic
• Added monitoring and execution simulation for route analysis
• Added orchestration service and controller endpoints
• Added request DTOs and entity models for liquidity state and arbitrage opportunities
• Added module documentation for overview and architecture

Checklist

• I have read the CONTRIBUTING guide.
• npm run lint passes.
• npx tsc --noEmit passes (no type errors).
• npm run build succeeds.
• npm test passes, and I added/updated tests for my change where it
  made sense.
• Any Stellar/Soroban network access goes through the stellar module
  services (no direct Horizon/RPC calls from feature modules).
• I did not commit secrets, private keys, or mainnet credentials.

Notes for Reviewers

This is the initial Liquidity Aggregator foundation. The module introduces the core structures and services needed for future route optimization and execution workflows. Review focus should be on the module boundary, naming consistency, and whether the service layering is aligned with the existing Nest architecture.