Write `indexer/README.md` with deployment and API reference

[Nursca]

Description
There is no README for the indexer. Operators deploying it in production and developers integrating with its API need documentation covering setup, configuration, database requirements, and API reference.

Requirements and context

• Architecture overview (how the indexer connects to Horizon and serves the API)
• Environment variable reference (database URL, Horizon URL, contract ID, port)
• Docker deployment instructions
• Full REST API reference with request/response examples for each endpoint
• Troubleshooting section for common issues (stream disconnection, migration failures)

Suggested execution

git checkout -b docs/indexer-readme

• Create indexer/README.md
• Link from org root README.md

Example commit message
docs(indexer): write comprehensive README with deployment and API reference

[gloskull]

Hi, I’d love to work on this issue. I have 4 years of experience across backend, frontend, full-stack, and smart contract development. I understand the task clearly and can deliver a clean, efficient, well-tested solution on time, with strong focus on code quality and maintainability. My PR will be submitted in under 10 hours.

[CHKM001]

@CHKM001 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Abeggg
Make i do this one biko
Nye m this task, maka osiso osiso finish finish
Thankss iye?

ℹ️ Repo Maintainers: To accept this application, review their application or assign @CHKM001 to this issue.

[probablyABug]

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

hi, i would like to work on this.

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

[0xBernny]

@0xBernny has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Because i can

ℹ️ Repo Maintainers: To accept this application, review their application or assign @0xBernny to this issue.

[drips-wave]

Congratulations, @0xBernny! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @0xBernny: 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.

Warning

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