✨ feat: implement API key authentication and user session management

web/app/api/files/write/route.ts

@@ -0,0 +1,31 @@
+import { NextRequest, NextResponse } from "next/server";
+import fs from "fs/promises";
+import path from "path";
+
+export async function POST(request: NextRequest) {
+  let body: { path?: string; content?: string };
+  try {
+    body = await request.json();
+  } catch {
+    return NextResponse.json({ error: "invalid JSON body" }, { status: 400 });
+  }
+
+  const { path: filePath, content } = body;
+  if (!filePath || content === undefined) {
+    return NextResponse.json(
+      { error: "path and content are required" },
+      { status: 400 }
+    );
+  }
+
+  const resolvedPath = path.resolve(filePath);
+
+  try {
+    await fs.writeFile(resolvedPath, content, "utf-8");
+    const stats = await fs.stat(resolvedPath);
+    return NextResponse.json({ success: true, size: stats.size });
+  } catch (err) {
+    const message = err instanceof Error ? err.message : "Unknown error";
+    return NextResponse.json({ error: message }, { status: 500 });
+  }
+}