Per-network deployment config validation

[truthixify]

Tier: S (½-1 day) Type: tooling

Context

good-first-issue

Scope

deploy.sh accepts testnet|futurenet|mainnet but doesn't validate the network passphrase, RPC URL, friendbot availability, or required env vars before starting. Add a preflight check.

Acceptance criteria

• New stellar/scripts/check-network.sh callable independently or as preflight
• For each network: verify passphrase, ping RPC, ping friendbot (if testnet), check identity exists
• Print summary table + exit non-zero on any failure
• Hook into deploy.sh as first step

Files to start with

• Preflight script + tests
• deploy.sh calls preflight
• Clear error messages when checks fail
• Documented in stellar/README.md

Why this matters

• stellar/deploy.sh