v0.4.0

Changelog

• 7752023 ci: gate the Rust billing crate
• c14e059 docs(design): add billing admin build plan
• 1a8fa8e docs(design): add escrow contract and billing/validator design notes
• 35d1af5 docs(design): port beacon routing + eRPC brief, reconcile tunneling plan with shipped VPN
• b03aeec docs(design): rename issued key prefix vk_ to jg_
• d45219f feat(billing): add the API-key manager
• 418d39c feat(billing): add the operator admin HTTP API
• 7ec1cab feat(billing): add the pricing runtime
• 0006445 feat(billing): scaffold store with schema and default pricing
• 8f298f4 feat(update): notify on a newer release, with disable and skip controls
• a432ef0 fix(executor): find docker when launched from Finder (extend local PATH)
• a31448d fix(panel): Docker readiness gate + auto-start, brand as Jumpgate, loading state
• d2eff1a refactor(update): replace "skip a version" with quiet-mode + on-demand check
• 5190ae5 test(billing): raise coverage across the crate