Self-hosted deployment guide

[truthixify]

Extra labels: writing, ops, stellar
Tier: M (2-4 days) | Type: writing

Context. Teams want to run their own instance of the contracts (private network, permissioned deployment). Doc the deployment flow end-to-end using the dry-run script (contracts issue #4).

Scope.

• New guides/ops/self-hosted-deployment.mdx.
• Prereqs (Soroban CLI, keypair, funded account).
• Run deploy-dryrun.sh walkthrough.
• Wiring contracts together.
• Publishing contract IDs to consumers.

Acceptance.

• Reviewer deploys on futurenet following only the guide
• Snippets pass CI
• Nav entry

Files. guides/ops/self-hosted-deployment.mdx (new).