refactor: migrate backoff crate to backon (#6718)

Replace backoff 0.4.0 with backon 1.6.0 for retry logic.

src-tauri/src/core/manager/lifecycle.rs

@@ -84,7 +84,7 @@ impl CoreManager {
     #[cfg(target_os = "windows")]
     async fn wait_for_service_if_needed(&self) {
         use crate::{config::Config, constants::timing, core::service};
-        use backoff::{Error as BackoffError, ExponentialBackoff};
+        use backon::{ConstantBuilder, Retryable as _};
 
         let needs_service = Config::verge().await.latest_arc().enable_tun_mode.unwrap_or(false);
 
@@ -92,16 +92,12 @@ impl CoreManager {
             return;
         }
 
-        let backoff = ExponentialBackoff {
-            initial_interval: timing::SERVICE_WAIT_INTERVAL,
-            max_interval: timing::SERVICE_WAIT_INTERVAL,
-            max_elapsed_time: Some(timing::SERVICE_WAIT_MAX),
-            multiplier: 1.0,
-            randomization_factor: 0.0,
-            ..Default::default()
-        };
+        let max_times = timing::SERVICE_WAIT_MAX.as_millis() / timing::SERVICE_WAIT_INTERVAL.as_millis();
+        let backoff = ConstantBuilder::default()
+            .with_delay(timing::SERVICE_WAIT_INTERVAL)
+            .with_max_times(max_times as usize);
 
-        let operation = || async {
+        let _ = (|| async {
             let mut manager = SERVICE_MANAGER.lock().await;
 
             if matches!(manager.current(), ServiceStatus::Ready) {
@@ -111,19 +107,19 @@ impl CoreManager {
             // If the service IPC path is not ready yet, treat it as transient and retry.
             // Running init/refresh too early can mark service state unavailable and break later config reloads.
             if !service::is_service_ipc_path_exists() {
-                return Err(BackoffError::transient(anyhow::anyhow!("Service IPC not ready")));
+                return Err(anyhow::anyhow!("Service IPC not ready"));
             }
 
-            manager.init().await.map_err(BackoffError::transient)?;
+            manager.init().await?;
             let _ = manager.refresh().await;
 
             if matches!(manager.current(), ServiceStatus::Ready) {
                 Ok(())
             } else {
-                Err(BackoffError::transient(anyhow::anyhow!("Service not ready")))
+                Err(anyhow::anyhow!("Service not ready"))
             }
-        };
-
-        let _ = backoff::future::retry(backoff, operation).await;
+        })
+        .retry(backoff)
+        .await;
     }
 }