Abstract hardcoded test account addresses out of README and deployment scripts

[nanaf6203-bit]

Problem Statement

README.md references CONTRACT_ACCOUNT=5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY in the env example. Other scripts use bare addresses.

Why it matters

Hardcoding a single dev account in README encourages reuse in production.

Technical Context

Use SURI=//Alice and node-key derivation; document polkadot-js flow.

Expected Outcome

README env example derives an account from SURI; scripts pull from .env.

Acceptance Criteria

1. grep -r '5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY' . returns 0 in production files.
2. README has an updated .env.example.
3. Scripts source .env.

Implementation Notes

Sed-replace + update README.

Files or modules likely to be affected

README.md, scripts/deploy.sh, scripts/build.sh.

Dependencies

None.

Difficulty level

EASY.

Estimated effort

XS (~30 min).

[Power70]

@Power70 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi Maintainer
I can work on this issue.
Kindly assign it to me.
Thank you.

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[Michealshodipo56]

@Michealshodipo56 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I would like to work on this kindly assign me

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[abdulrcrtw]

@abdulrcrtw has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi, I'd like to work on this issue.

I have hands-on experience with backend development, databases, and API design, as well as frontend work with React and modern CSS. I write tested, maintainable code and enjoy contributing to open source projects.

I've reviewed the issue and I'm confident I can implement a solid solution while following the project's conventions.

Happy to get started right away if assigned — looking forward to contributing.

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