Add stellar-cli sandbox lifecycle test

[Killerjunior]

📌 Description

Adds a CI integration job that runs the deployed contract against a real stellar-cli local sandbox. The new script starts a local Stellar container, deploys the contract WASM and native asset contract, then exercises the happy-path lifecycle: initialize, create campaign, verify campaign, contribute, withdraw funds, and assert final on-chain state.

🔗 Related Issues

Closes #501

🧪 Changes Made

• Bug fix
• New feature
• Refactor
• Documentation update

✅ Checklist

• Code compiles successfully
• Tests added/updated and passing
• Linting passes (no warnings/errors)
• Documentation updated (if required)
• No breaking changes (or clearly documented)

⚠️ Breaking Changes

None.

📸 Screenshots (if applicable)

Not applicable.

🧩 Additional Notes

The sandbox test is implemented in scripts/stellar_cli_happy_path.sh and wired into .github/workflows/ci.yml as the stellar-cli-sandbox job. I could not execute the sandbox locally because this Windows environment does not have Bash or stellar installed; CI will run it on Ubuntu.

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[davidmaronio]

the sandbox lifecycle script itself is reasonable (set -euo pipefail, a network health-wait loop, an exit trap to stop the container, isolated XDG_CONFIG_HOME). the fmt/clippy/test reds are from a stale base that doesn't compile (missing token/uses_milestones on CreateCampaignParams, duplicate set_emergency_pause_signers), none of that is in your diff. rebase onto current main and it should go green. minor: the new job runs cargo install --locked stellar-cli unpinned, pinning a version would make it reproducible.