feat(contracts): publish testnet contract registry (#410)

[JohnOluB]

What this PR does

Resolves #410 by introducing contracts/registry/ — a single source of truth for all Soroban contract addresses and initialization configuration on Stellar Testnet.

Files added

File | Purpose -- | -- testnet.registry.json | Primary machine-readable registry (JSON). Stores contract IDs, deployer addresses, WASM hashes, timestamps, git SHAs, and init args. testnet.env | Environment-style mirror for .env consumption by frontend/backend. index.ts | Type-safe TypeScript loader — getContractId('aid_escrow') throws clearly if the contract isn't deployed yet. update-registry.sh | Run after soroban contract deploy to auto-populate all REPLACE_WITH_* placeholders with real values + current git SHA. abi/ | Directory for ABI JSON files generated by soroban contract inspect. README.md | Contributor guide covering structure, updating, code usage, and security notes.

How to update after a deploy

bash

./contracts/registry/update-registry.sh \
  --contract-id  C...   \
  --deployer     G...   \
  --wasm-hash    abc123 \
  --admin        G...

Checklist

• Machine-readable JSON format
• Records contract ID, deployer, WASM hash, init args
• Timestamp + git commit SHA captured
• Easy for contributors to update (script + manual instructions)
• Type-safe TS helper for app consumption
• No secrets committed (public keys only)

closes #410

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You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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[Cedarich]

Please fix workflow