swarm: prevent interacting with read-only conversations

Read-only conversation has:
- a lock icon in the smartlist item
- no message send bar in the chat view
- no call actions available from the chat view header
- no call actions available from the smartlist context menu
- no double click to call

Change-Id: I0497b94038b450f0a0a22fc007de1281b7b2214d
Gitlab: #475