Summary

• Pre-check server lock status before dispatching any mutating action (delete, reboot, resize, rename, etc.)
• Show a clear sticky hint ("Server is locked. Unlock it first with Ctrl+L.") instead of letting the API reject with a confusing error
• Read-only actions (console log, console URL, action history, copy SSH) and lock/unlock itself remain unguarded

Closes #55

Test plan

• Select a locked server, press any mutating key (e.g., Ctrl+D for delete) — verify sticky hint appears and no confirmation modal opens
• Select a locked server, press Ctrl+L — verify lock/unlock toggle still works
• Select a locked server, press read-only keys (L, a, V, y) — verify they still work
• Bulk-select servers including a locked one, press a mutating key — verify it's blocked
• Select an unlocked server, press mutating keys — verify normal behavior unchanged