[client] Add sleep state tracking to handle wakeup/sleep events reliably (#4894)

Adds a new NotifyOSLifecycle RPC and server handler to centralize OS sleep/wake handling, introduces Server.sleepTriggeredDown for coordination, updates client UI to call the new RPC, and adjusts the internal sleep event enum zero-value semantics.

client/proto/daemon.proto

@@ -24,7 +24,7 @@ service DaemonService {
   // Status of the service.
   rpc Status(StatusRequest) returns (StatusResponse) {}
 
-  // Down engine work in the daemon.
+  // Down stops engine work in the daemon.
   rpc Down(DownRequest) returns (DownResponse) {}
 
   // GetConfig of the daemon.
@@ -93,9 +93,26 @@ service DaemonService {
 
   // WaitJWTToken waits for JWT authentication completion
   rpc WaitJWTToken(WaitJWTTokenRequest) returns (WaitJWTTokenResponse) {}
+
+  rpc NotifyOSLifecycle(OSLifecycleRequest) returns(OSLifecycleResponse) {}
 }
 
 
+
+message OSLifecycleRequest {
+  // avoid collision with loglevel enum
+  enum CycleType {
+    UNKNOWN = 0;
+    SLEEP = 1;
+    WAKEUP = 2;
+  }
+
+  CycleType type = 1;
+}
+
+message OSLifecycleResponse {}
+
+
 message LoginRequest {
   // setupKey netbird setup key.
   string setupKey = 1;