[Backend] Transaction Enrichment Structuring

[Olowodarey]

Background & Context: Raw databases hold amount: 100000000 but users expect to read 100.00 USDC.
Description: The payload interceptor must apply native mathematics correctly spacing decimal properties prior to resolving the controller logic.
Acceptance Criteria:

• Construct explicit formatter logic attaching asset mapping symbols evaluating Stellar contract precision parameters intelligently rendering UI outputs exactly (e.g. amountFormatted: "$500.00" alongside base parameters).
• Dynamically attach canonical Stellar Expert exploration links directly utilizing the raw txHash.
  Target Files: backend/src/common/interceptors/transaction-formatting.interceptor.ts.