Validate SOROBAN_RPC_URL and network passphrase pairing at boot

[EmmanuelOchaje]

Context

Mismatched RPC and passphrase would silently sign for the wrong network.

Task

• Cross-check known networks in env.validation.ts

Acceptance criteria

• Bad pair fails startup
• Spec added

This issue is self-contained and can be picked up independently of any other open issue.

[Adeiza15]

@Adeiza15 has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Hi Maintainer, I've thoroughly reviewed the scope of this issue and feel confident handling it. I’d appreciate it if you could assign it to me

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Adeiza15 to this issue.

[UFObject247]

@UFObject247 has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Hi maintainer, I'd like to work on this issue.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @UFObject247 to this issue.

[drips-wave]

Congratulations, @UFObject247! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on September 30, 2026.

🧑‍💻 @UFObject247: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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