Add provider catalog sorting for stable API responses

[emrekayat]

Goal

Make the provider catalog deterministic so demos, tests, and clients receive stable ordering across runs.

Scope

• Sort providers in the public catalog response by category, then price, then provider id.
• Keep provider payload shape unchanged.
• Keep disabled-provider filtering behavior unchanged.
• Add or update a focused public route/provider test.

Acceptance criteria

• GET /api/providers returns providers in deterministic category/price/id order.
• Existing provider fields are unchanged.
• The test covers at least one tie-breaker by provider id or price.
• npm test --workspace @query402/api -- src/routes/public.test.ts src/providers/registry.test.ts passes.
• npm run typecheck --workspace @query402/api passes.

Notes

This is intended to be a small sorting-only change, not a provider model redesign.

[annacodervibe]

@annacodervibe has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would like to work on this issue. I have experience with Rust and Soroban smart contract development. I will follow the acceptance criteria and add tests. Excited to contribute. Kindly assign.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @annacodervibe to this issue.

[drips-wave]

Congratulations, @annacodervibe! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @annacodervibe: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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