add missing license headers (#68)

adding missing license headers to source code files like` *.go, *.sh and
Dockerfile and Makefile`

Author: gauravkr19

Makefile

@@ -1,3 +1,17 @@
+#  Copyright 2025 The Nephio Authors.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
 GO_VERSION ?= 1.20.2
 GOLANG_CI_VER ?= v1.52
 GOSEC_VER ?= 2.15.0