Add defensive nil checks in ThreadSafeAgent.Close() to prevent panic
when agent field is nil. This can occur during Windows suspend/resume
when network interfaces are disrupted or the pion/ice library returns
nil without error.
Also capture agent pointer in local variable before goroutine execution
to prevent race conditions.
Fixes service crashes on laptop wake-up.
updates the logging implementation to use the netbird logger for both ICE and gRPC components. The key changes include:
- Introducing a gRPC logger configuration in util/log.go that integrates with the netbird logging setup.
- Updating the log hook in formatter/hook/hook.go to ensure a default caller is used when not set.
- Refactoring ICE agent and UDP multiplexers to use a unified logger via the new getLogger() method.
