feat: add BLE watchdog constants and connection event

src-tauri/src/lib.rs

@@ -6,6 +6,7 @@ mod telemetry;
 mod commands;
 
 use std::sync::{Arc, Mutex, RwLock};
+use std::time::Duration;
 
 use futures::StreamExt;
 use serde::Serialize;
@@ -35,6 +36,20 @@ struct BatteryEvent {
     percent: u8,
 }
 
+// Watchdog: how long without telemetry before the connection is considered dead.
+const WATCHDOG_STALE_TIMEOUT: Duration = Duration::from_secs(5);
+// How many times to retry reconnect before giving up.
+const RECONNECT_MAX_ATTEMPTS: u32 = 5;
+// Base backoff between reconnect attempts.
+const RECONNECT_BACKOFF: Duration = Duration::from_secs(2);
+
+#[derive(Clone, Serialize)]
+struct ConnectionEvent {
+    device_id: String,
+    category: String,
+    status: &'static str, // "reconnecting" | "reconnected" | "gave_up"
+}
+
 #[tauri::command]
 async fn init(app: AppHandle) -> Result<(), String> {
     let repo = scan_and_classify(&app).await.map_err(|e| e.to_string())?;