Add Next.js client app with Prisma and auth

Introduce a new 'client' Next.js app scaffold: configuration files (next.config.ts, eslint.config.mjs, postcss, tsconfig), Prisma config and schema, app routes including NextAuth API and server actions, session/provider utilities, proxy, public assets, README and .gitignore. Also add IDE project files under .idea and a root README to initialize the repository structure for development.

.idea/modules.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/.idea/XRayPDF.iml" filepath="$PROJECT_DIR$/.idea/XRayPDF.iml" />
+    </modules>
+  </component>
+</project>