fix: proxy subscribe through Next.js API route to avoid network permission prompt

Browser was requesting local network access for the Tailscale URL.
Now both forms POST to /api/subscribe which proxies server-side
to the leads-api container.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

site/app/api/subscribe/route.ts

@@ -0,0 +1,18 @@
+import { NextRequest, NextResponse } from "next/server";
+
+const API_URL = process.env.LEADS_API_URL || "http://leads-api:3400";
+
+export async function POST(req: NextRequest) {
+  try {
+    const body = await req.json();
+    const res = await fetch(`${API_URL}/subscribe`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify(body),
+    });
+    const data = await res.json();
+    return NextResponse.json(data, { status: res.status });
+  } catch {
+    return NextResponse.json({ error: "upstream error" }, { status: 502 });
+  }
+}

site/app/newsletter-form.tsx

@@ -2,8 +2,6 @@
 
 import { useState } from "react";
 
-const API_URL = "https://alezmad-nuc.tail58f5ad.ts.net";
-
 export function NewsletterForm({ project = "cladm" }: { project?: string }) {
   const [email, setEmail] = useState("");
   const [status, setStatus] = useState<"idle" | "loading" | "ok" | "error">("idle");
@@ -14,7 +12,7 @@ export function NewsletterForm({ project = "cladm" }: { project?: string }) {
     if (!email.trim()) return;
     setStatus("loading");
     try {
-      const res = await fetch(`${API_URL}/subscribe`, {
+      const res = await fetch("/api/subscribe", {
         method: "POST",
         headers: { "Content-Type": "application/json" },
         body: JSON.stringify({ email: email.trim(), project }),

site/app/subscribe-modal.tsx

@@ -2,8 +2,6 @@
 
 import { useState, useEffect, useRef, useCallback } from "react";
 
-const API_URL = "https://alezmad-nuc.tail58f5ad.ts.net";
-
 type Phase = "boot" | "prompt" | "sending" | "done";
 
 const BOOT_LINES = [
@@ -86,7 +84,7 @@ export function SubscribeModal() {
     setPhase("sending");
     setError("");
     try {
-      const res = await fetch(`${API_URL}/subscribe`, {
+      const res = await fetch("/api/subscribe", {
         method: "POST",
         headers: { "Content-Type": "application/json" },
         body: JSON.stringify({ email: email.trim(), project: "cladm" }),