feat: create deployment automation scripts

[starkiVector-090]

add automated deployment scripts and update deployment docs

Replaces manual deployment steps with two scripts:

• scripts/deploy.sh — unified testnet/mainnet deployment with pre-flight checks (Rust version, wasm target, Stellar CLI), environment confirmation prompt, mainnet admin key verification, --upgrade mode
  for Wasm-only upgrades preserving on-chain state, automatic post-deployment verification, and a timestamped report saved to reports/.
• scripts/verify-deployment.sh — standalone post-deployment verifier that calls five read-only contract functions and exits non-zero on any failure.

docs/deployment.md updated to document the automated flow, upgrade procedure, rollback options (Wasm rollback, contract pause, oracle rotation), and verification checks.

closes #739

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