test(domain): BDD for video status, token, share link

[crrow]

Context

Write cucumber-rs BDD feature files and step definitions for core domain models.

Acceptance Criteria

• features/video_status.feature — state machine transitions
• features/connection_token.feature — sign, verify, expiry, action scoping
• features/share_link.feature — creation with s_ prefix, expiry, uniqueness
• All steps implemented in tests/steps/
• rara-bdd coverage: zero missing steps
• cargo test --test bdd: all pass