Initial commit: EGBE chatbot template

Stripped from vercel/chatbot (Apache 2.0):
- Dropped @vercel/* packages and AI Gateway
- Removed artifacts feature (code/text/sheet/image side panel)
- Switched AI provider to @ai-sdk/openai-compatible -> EGBE LiteLLM
- Replaced Vercel Blob upload with data URLs
- Dropped Redis resumable streams and rate limiter (in-memory now)
- Added Dockerfile (Next.js standalone) + entrypoint that runs migrations
- Wired DATABASE_URL, EGBE_AI_API_URL/KEY, NEXT_PUBLIC_BASE_URL for app-deploy.sh

app/(auth)/api/auth/[...nextauth]/route.ts

@@ -0,0 +1 @@
+export { GET, POST } from "@/app/(auth)/auth";

app/(auth)/api/auth/guest/route.ts

@@ -0,0 +1,26 @@
+import { NextResponse } from "next/server";
+import { getToken } from "next-auth/jwt";
+import { signIn } from "@/app/(auth)/auth";
+import { isDevelopmentEnvironment } from "@/lib/constants";
+
+export async function GET(request: Request) {
+  const { searchParams } = new URL(request.url);
+  const rawRedirect = searchParams.get("redirectUrl") || "/";
+  const redirectUrl =
+    rawRedirect.startsWith("/") && !rawRedirect.startsWith("//")
+      ? rawRedirect
+      : "/";
+
+  const token = await getToken({
+    req: request,
+    secret: process.env.AUTH_SECRET,
+    secureCookie: !isDevelopmentEnvironment,
+  });
+
+  if (token) {
+    const base = process.env.NEXT_PUBLIC_BASE_PATH ?? "";
+    return NextResponse.redirect(new URL(`${base}/`, request.url));
+  }
+
+  return signIn("guest", { redirect: true, redirectTo: redirectUrl });
+}