Add admin panel, gallery, and security hardening.

Replace forgeable cookie auth with signed JWT sessions, protect admin APIs, add input validation, and improve Docker deployment config.

src/app/api/auth/logout/route.ts

@@ -0,0 +1,14 @@
+import { NextResponse } from "next/server";
+import { getSessionCookieOptions, SESSION_COOKIE } from "@/lib/session";
+
+export async function POST() {
+    const response = NextResponse.json({ success: true });
+
+    response.cookies.set({
+        ...getSessionCookieOptions(0),
+        name: SESSION_COOKIE,
+        value: "",
+    });
+
+    return response;
+}