[Docs] Add a deployed contract address registry doc per network

[Akpolo]

https://t.me/+DOylgFv1jyJlNzM0

Why this matters

The deploy tooling (scripts/deploy-config.json, scripts/deploy.ts) references the four contract WASM artifacts, and the backend/frontend read contract IDs from env, but there is no committed registry of which contract IDs are deployed on which network (testnet/futurenet/mainnet). Contributors wiring the backend or running E2E flows have to ask in chat for the current testnet IDs. A single source-of-truth table avoids repeated onboarding friction and mismatched envs.

Acceptance criteria

• New doc (e.g. docs/deployed-contracts.md) with a per-network table: contract name -> deployed contract ID -> deploy date / version
• Include the public testnet IDs currently in use (loan_manager, lending_pool, remittance_nft, multisig_governance, token)
• Note which env vars consume each ID (backend and frontend)
• Link from README and CONTRIBUTING

Files to touch

• docs/deployed-contracts.md (new)
• README.md, CONTRIBUTING.md

Out of scope

• Automating address publication from the deploy script
• Committing any secrets/keys

[K1NGD4VID]

@K1NGD4VID has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

hello maintainer, i would like to work on this issue

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