feat: channel encryption indicator in peer / dial UI

[krwg]

Summary

UI half of mesh TCP encryption: show whether the live channel to a peer is encrypted or fell back to legacy plaintext.

UX

• Lock / status affordance beside peer name in peers + dial views (same pattern as existing presence/status helpers)
• Tooltip copy EN/RU: encrypted vs “peer on old protocol — not protected”
• Driven by trust/session state from the encrypted-transport work

Depends on

Encrypted TCP session flag from the mesh encryption issue (can stub UI behind a session field).

Acceptance

• Encrypted and plaintext states distinguishable in UI
• i18n EN/RU
• No false “secure” badge on fallback plaintext