[Docs] Author a system architecture overview with diagrams connecting contracts, backend, indexer, and frontend

[grantfox-oss]

Telegram (ask questions / claim the issue here first): https://t.me/+DOylgFv1jyJlNzM0

Why this matters

The repo has scattered design docs (DESIGN.md, LANDING_PAGE_DESIGN.md) and three wiki pages, but no single architecture overview that shows how the Soroban contracts, the backend API, the event indexer, the Postgres database, and the Next.js frontend fit together. New contributors cannot form a mental model of the system.

Acceptance criteria

• Add architecture.md with a high-level component diagram (mermaid) of contracts, backend, indexer, DB, and frontend
• Describe the request and event data flows (user action -> backend -> contract -> indexer -> DB -> frontend)
• Link out to the contract reference, API reference, and indexer-sync-flow wiki pages
• List the trust boundaries and the major external dependencies (Stellar RPC, Redis, Sentry)

Files to touch

• architecture.md (new)
• wiki/README.md
• wiki/indexer-sync-flow.md

Out of scope

• Per-service deep dives (separate issues)
• Sequence diagrams for every endpoint

[gloskull]

Hello, I have 4 years of experience delivering solutions for projects like this, covering backend, frontend, and smart contract development. After carefully reviewing your requirements, I have a clear understanding of the task and am confident in my ability to deliver a clean, efficient, and thoroughly tested solution on time. I prioritize code quality, maintainability, and industry best practices throughout the development process.

[bamiebot-maker]

kindly assign this task to me I am read to work on the dox

[Delightech28]

I'd like to work on this

[grantfox-oss]

🦊 GrantFox — @Delightech28 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 #1)
2. Your PR will be reviewed by the LabsCrypt maintainers

Good luck! Track your progress on GrantFox.