Design and implement multi-chain MembershipNFT support (deferred area)

[Lakes41]

Difficulty: Expert
Type: feature

Background
The README explicitly lists "Multi-chain support (current: EVM only)" as a deferred area, and notes that after deploying MembershipNFT, operators set a single MEMBERSHIP_NFT_ADDRESS and CHAIN_ID in .env — implying the current architecture assumes one contract on one chain.

Problem
Communities that deploy MembershipNFT on more than one EVM chain (e.g., mainnet + an L2) have no way to represent that in the data model or access API, since membership resolution is implicitly single-chain.

Expected outcome
The data model and access API support multiple (chainId, contractAddress) pairs per community, with membership resolution correctly disambiguating a wallet's memberships across chains, and packages/contracts exposing per-chain ABI/address configuration instead of a single global address.

Suggested implementation

• Extend the memberships/communities Prisma schema to key membership records by (chainId, contractAddress, tokenId) rather than assuming a single global contract.
• Update packages/contracts to support a registry of { chainId, address, abi } entries per community instead of a single MEMBERSHIP_NFT_ADDRESS/CHAIN_ID pair.
• Update the event-ingestion module (see the reorg-handling issue, if implemented, or the current test-simulated flow) to run per configured chain and correctly attribute events to the right (chainId, contractAddress).
• Update /v1/memberships/:wallet and /v1/access/check to correctly aggregate or disambiguate memberships across chains for a single wallet.
• Update .env.example, README, and docs/openapi.json to reflect the new multi-chain configuration model, including a migration guide from the current single-chain setup.

Acceptance criteria

• A community can be backed by MembershipNFT deployments on more than one chain simultaneously
• Membership resolution correctly attributes and aggregates per-chain state
• Existing single-chain deployments continue to work via a documented migration path
• README/.env.example/OpenAPI updated

Likely affected files/directories

• packages/contracts/
• apps/access-api/prisma/schema.prisma
• apps/access-api/src/routes/
• .env.example
• README.md, docs/openapi.json

[Chigybillionz]

please assign me to this