Remove merge-swagger.sh and simplify doc generation pipeline

[gandalf-at-lerian]

Context

The merge-swagger.sh script was originally created to merge separate Swagger specs from the onboarding and transaction modules into a unified spec. Since both modules have been consolidated into a single ledger component, the merge step is no longer necessary — swag init on the ledger component produces a complete spec directly.

Current pipeline

1. swag init generates ledger_swagger.json
2. merge-swagger.sh patches metadata (title, version, host, securityDefinitions), generates docs.go with embedded JSON, converts to YAML, and cleans up intermediates

Proposed pipeline

1. swag init --outputTypes json,yaml generates swagger.json, swagger.yaml, and docs.go directly — no post-processing

Changes needed

• Update main.go swagger annotations:
  • @title → Midaz Ledger API (Unified)
  • @host → localhost:3002
  • @description → match current production description
  • Add @securityDefinitions.apikey BearerAuth
  • Version should come from a single source (currently hardcoded in both main.go and .env)
• Update components/ledger/Makefile generate-docs target to call swag init directly instead of the merge script
• Delete components/ledger/scripts/merge-swagger.sh
• Regenerate specs and verify output matches current production spec

Notes

• swagger.go already supports runtime overrides via env vars (SWAGGER_TITLE, SWAGGER_HOST, etc.), so hardcoded defaults in annotations are safe
• openapi.yaml (OAS 3.0) has no automated generation pipeline today — that's a separate concern
• The jq dependency for doc generation can be dropped after this change