Chat was only reachable via an offer's 'Message' button, and the drawer 'Chat'
sat on 'coming soon' — so messaging/trust were effectively hidden.
- MessageStore keeps a conversation index (the keystore has no key enumeration)
and exposes conversations() — peers newest-active-first with their last line.
- ChatListScreen: the messages inbox (tap a conversation → /chat/:pubkey).
- Drawer 'Chat' is now a live destination -> /messages (gated like Market).
- i18n en/es/pt. conversations() covered by a plain test (no widget hang).
Analyzer clean.
Messages were in-memory only — gone on leaving the conversation.
- MessageStore: keystore-backed (no plaintext), a capped per-peer JSON list
(last 200). Simple; the encrypted Drift DB is the eventual home at scale.
- MessagesCubit: loads saved history on start (subscribes FIRST, then loads, so
a message arriving during the load isn't dropped) and persists every sent and
received message. Wired via DI + TaneApp(messageStore).
Tests (plain 'test', no hang risk): MessageStore round-trip/per-peer/cap, and a
cubit test that reopens a fresh cubit and sees the saved conversation. Analyzer
clean; run 'flutter test' locally to confirm.
