Add contract configuration validation

[Lakes41]

The contracts helper reads MEMBERSHIP_NFT_ADDRESS and CHAIN_ID directly from environment variables. Add validation so invalid or missing contract configuration fails clearly when on-chain features are used.

Suggested tasks

• Validate that MEMBERSHIP_NFT_ADDRESS is a valid EVM address when required
• Validate that CHAIN_ID is a valid number
• Add a helper such as getContractAddresses()
• Avoid silently returning an empty contract address in production
• Add tests for valid and invalid environment values
• Document the expected contract environment variables

Acceptance criteria

• Invalid contract configuration returns a clear error
• Production usage cannot silently proceed with an empty contract address
• Contract configuration validation is tested

[titilayo967]

I've built contract configuration validation in Node.js backends before, and I can add a getContractAddresses() helper that validates MEMBERSHIP_NFT_ADDRESS as a proper EVM address and CHAIN_ID as a valid number — with clear errors on invalid or missing values so production never silently proceeds with an empty address.

[Dwifax]

Hi — I'm Dwifax. I've cloned guildpass-core and read the contracts package. The current config in packages/contracts/src/index.ts has silent fallbacks: an empty default for membershipNFT and parseInt('foo') returning NaN for chainId, both shipped to consumers without errors.

Plan (2–3 days):

1. Replace bare process.env reads with getContractAddresses() that validates at module load — Zod-style schema: membershipNFT matches ^0x[0-9a-fA-F]{40}$, chainId positive int (1–2^31−1). Throw a typed InvalidContractConfigError on failure (no silent NaN, no empty defaults).
2. Export validateContractConfig(input) helper so access-api can validate env at boot.
3. Add vitest (no test framework in this package yet) — tests for: invalid address, missing chainId, MEMBERSHIP_NFT_ADDRESS=0xnotanaddr, valid case.
4. Update .env.example with format docs for both vars.

Same shape as DRE App #1 (config/env validation, merged).

Available now, can open the PR within 48h. Happy to swap validation lib (Zod vs yup vs hand-rolled regex) if you have a preference.

[grantfox-oss]

🦊 GrantFox — @Dwifax 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 #7)
2. Your PR will be reviewed by the Adamantine-guild maintainers

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@Dwifax's PR #37 was approved and merged by @Lakes41.

🏆 @Dwifax: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (118 total points). Track your full progress on GrantFox.

👏 Great work, @Dwifax! Keep contributing to Adamantine-guild.