fix(logging): expand tilde in auth-dir and log resolution errors

- Use util.ResolveAuthDir to properly expand ~ to user home directory
- Fixes issue where logs were created in literal "~/.cli-proxy-api" folder
- Add warning log when auth-dir resolution fails for debugging

Bug introduced in 62e2b67 (refactor(logging): centralize log directory
resolution logic), where strings.TrimSpace was used instead of
util.ResolveAuthDir to process auth-dir path.

internal/logging/global_logger.go

@@ -131,7 +131,10 @@ func ResolveLogDirectory(cfg *config.Config) string {
 		return logDir
 	}
 	if !isDirWritable(logDir) {
-		authDir := strings.TrimSpace(cfg.AuthDir)
+		authDir, err := util.ResolveAuthDir(cfg.AuthDir)
+		if err != nil {
+			log.Warnf("Failed to resolve auth-dir %q for log directory: %v", cfg.AuthDir, err)
+		}
 		if authDir != "" {
 			logDir = filepath.Join(authDir, "logs")
 		}