Fix Stellar Wave issue set: 400, 401, 402, 403

[edehvictor]

Closes #400
Closes #401
Closes #402
Closes #403

Summary

• Added a reusable protected-route request helper and applied it to two protected-route integration tests.
• Added response timestamp handling for creator detail responses and expanded the cache-header regression test.
• Added a string truncation helper and used it in creator profile writes before persistence.
• Added contributor guidance for indexer changes.

Testing

• git diff --check
• Reviewed the final diff for the new helper, tests, docs, and creator profile service changes.

Notes

• Local pnpm tooling is not installed in this environment, so I could not run the repository test scripts here.

[drips-wave]

@edehvictor Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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