feat: add support for NO_DNA

[AtoMicKraK1n]

Description

• Adds NO_DNA detection to CLI
• Disables interactive UX in NO_DNA mode for key paths touched here
• Prevents interactive cloud login flow when NO_DNA=1 (returns clear actionable error instead).
• Forces non-TUI behavior for simnet start in NO_DNA mode.
• Adds unit tests for env parsing and updates top-level --help text to document automation mode.

Validation

• cargo fmt
• cargo check -p surfpool-cli
• cargo test -p surfpool-cli no_dna
• manual: NO_DNA=1 ./target/debug/surfpool cloud start is non-interactive and errors clearly.

#569

[MicaiahReid]

Hey @AtoMicKraK1n, thanks for the PR. We've actually removed the cloud crate - can you rebase main?

[AtoMicKraK1n]

Hey @AtoMicKraK1n, thanks for the PR. We've actually removed the cloud crate - can you rebase main?

Rebased onto latest and pushed! Could you please take another look?