v0.0.40: reliability — call reload, ETH cache prefill, 10 server tests

Call state reload on restart:
- Loads Ringing/Active calls from sled into active_calls on startup
- Expires calls older than 24h automatically

TUI sender ETH cache prefill:
- prefill_eth_cache() resolves all known contacts on poll_loop start
- First message from known contacts now shows ETH address immediately

Server integration tests (10 new):
- push_to_client offline/online
- register_ws + connection cap (5 max)
- is_online + device_count
- kick_device + revoke_all_except
- deliver_or_queue offline/online
- call state lifecycle
- list_devices

155 tests passing (was 135)

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

warzone/crates/warzone-server/Cargo.toml

@@ -28,3 +28,7 @@ bincode.workspace = true
 sha2.workspace = true
 reqwest = { workspace = true, features = ["rustls-tls", "json"] }
 tokio-tungstenite.workspace = true
+
+[dev-dependencies]
+tempfile = "3"
+tokio = { workspace = true, features = ["test-util"] }