Fix/address endpoints

[Zalgia-Saga]

Summary

This PR adds the missing address-scoped holdings and compliance endpoints requested in the issue set and updates the public API docs to match the implementation.

Included changes

• Add GET /v1/holders/:address to return all assets and balances held by a Stellar address.
• Add GET /v1/compliance/:address to return the per-address compliance view across assets currently held by the address.
• Expose the new routes in the API router and root metadata.
• Update the OpenAPI document and MDX overview docs so the new endpoints are documented consistently.

Why

The API already supported asset-level holder and compliance summaries, but it did not expose the per-address lookup patterns needed by clients and docs examples. These additions keep the implementation small and aligned with the current API structure while covering the missing use cases.

Testing

• cd api && cargo test --quiet

Related issues

closes #256
closes #258
closes #259
closes #275

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