Fix: Add .dockerignore to prevent .env.local from polluting Docker build

.dockerignore

@@ -0,0 +1,13 @@
+node_modules
+.next
+.git
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+npm-debug.log
+yarn-debug.log
+yarn-error.log
+.vercel
+.vscode
+.idea