client: verbose CLI output, TOML config in APPDATA, desktop install

- install.ps1: place exe on Desktop instead of TEMP, start with visible window
- main.rs: banner on startup, [CMD]/[OK]/[ERR] prefixed logs with HH:MM:SS timestamps
- Config: switch from JSON to TOML (config.toml in %APPDATA%\helios-remote\)
- First-run wizard prompts for Relay URL + API Key (relay_code -> api_key)
- Add chrono + toml deps to Cargo.toml

crates/client/Cargo.toml

@@ -13,6 +13,8 @@ tokio-tungstenite = { version = "0.21", features = ["connect", "native-tls"] }
 native-tls = { version = "0.2", features = [] }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
+toml = "0.8"
+chrono = "0.4"
 helios-common = { path = "../common" }
 dirs = "5"
 tracing = "0.1"