v0.0.19: contact list + message history (local, persistent)

Storage:
- contacts sled tree: auto-tracked on send/receive
  - fingerprint, alias, first_seen, last_seen, message_count
- history sled tree: all messages stored locally
  - key: hist:<peer_fp>:<timestamp>:<uuid> for ordered scan
  - sender, text, is_self, timestamp

TUI commands:
- /contacts or /c — list all contacts (sorted by most recent)
  Shows alias, fingerprint, message count
- /history or /h — show last 50 messages with current peer
- /h <fingerprint> — show history with specific peer

Auto-tracking:
- On send: touch_contact + store_message (is_self=true)
- On receive: touch_contact + store_message (is_self=false)
- Both KeyExchange and Message variants tracked

Backup: contacts + history included in export_all (encrypted backup).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/Cargo.toml

@@ -9,7 +9,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.0.18"
+version = "0.0.19"
 edition = "2021"
 license = "MIT"
 rust-version = "1.75"