fix: stderr namespace filter, fileInfo depth, panic guard, race safety

- fix(stderr): CreateClient() with no args so stderr sees all namespaces,
  not just 'default'. Previously namespaced logs were invisible on stderr.
- fix(logger): fileInfo depth offset to 2+FileInfoDepth so Logger methods
  report the actual caller, not the log package itself. Default depth (0)
  now correctly shows caller file:line.
- fix(panic): guard args[0] access with len(args) > 0 instead of >= 0.
  Panic/Panicf/Panicln would index out of range when called with no args.
- fix(createLog): nil/initialized check before channel send to prevent
  race with concurrent Destroy calls.
- chore: bump go.mod to 1.25.6

go.mod

@@ -1,5 +1,5 @@
 module github.com/taigrr/log-socket/v2
 
-go 1.25.4
+go 1.25.6
 
 require github.com/gorilla/websocket v1.5.3