docs: add README, LICENSE, and configure automated license headers

app/src/main/java/com/aryan/reader/data/PurchaseEntities.kt

@@ -1,3 +1,22 @@
+/*
+ * Episteme Reader - A native Android document reader.
+ * Copyright (C) 2026 Episteme Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * Electronic mail: epistemereader@gmail.com
+ */
 package com.aryan.reader.data
 
 /**