[23] Implement `stellar.toml` endpoint

[EmeditWeb]

Problem

There is no GET /.well-known/stellar.toml endpoint. Wallets and indexers that auto-discover Stellar projects (Lobstr directory, StellarExpert) cannot find StepFi's federation file from the API domain.

Context

stellar.toml is the discoverability standard for Stellar projects — it advertises org info, contract IDs, and curated asset metadata. Wallets read it to display the project name and verify contract addresses.

Before Starting

Read these context files first:

• context/architecture-context.md
• context/code-standards.md
• context/progress-tracker.md
• src/modules/health/health.controller.ts

What To Build

1. Add a StellarTomlController (or extend HealthController) exposing GET /.well-known/stellar.toml.
2. Set Content-Type: text/plain; charset=utf-8 and Access-Control-Allow-Origin: *.
3. Body content: org name, website, github, contracts block listing CREDITLINE_CONTRACT_ID, LIQUIDITY_POOL_CONTRACT_ID, REPUTATION_CONTRACT_ID, VENDOR_REGISTRY_CONTRACT_ID, all read from ConfigService.
4. Cache the response in memory with 1-hour TTL (cheap to regenerate, but no need to do it per request).
5. Add Swagger decorators marking it as a static metadata endpoint.
6. Add e2e test asserting status 200, content-type text/plain, and contract IDs present.

Files To Touch

• src/modules/health/stellar-toml.controller.ts
• src/modules/health/health.module.ts
• test/e2e/stellar-toml.e2e-spec.ts

Acceptance Criteria

• GET /.well-known/stellar.toml returns 200 with text/plain body
• Body includes all 4 contract IDs
• CORS allows * for this endpoint specifically
• Cached in memory for 60 minutes
• E2E test verifies content
• Swagger lists the endpoint

Mandatory Checks Before PR

• npm run build passes with zero TypeScript errors
• No new any types introduced anywhere
• Full Swagger @apioperation + @apiresponse decorators on any new endpoints
• New migration file created for any schema changes
• context/progress-tracker.md updated

[peter941221]

I'd like to work on this.

[deslawson]

This goes in line with my experience, please assign

[grantfox-oss]

🦊 GrantFox — @deslawson has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #15)
2. Your PR will be reviewed by the StepFi-app maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@deslawson's PR #45 was approved and merged by @EmeditWeb.

🏆 @deslawson: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (48 total points). Track your full progress on GrantFox.

👏 Great work, @deslawson! Keep contributing to StepFi-app.