feat: forward leads to central lead-inbox (ADR 012)

handleLead forwards to LEAD_INBOX_URL/v1/leads (DE field aliases map
server-side); local ndjson/csv stays as fallback. No-op until
LEAD_INBOX_URL/LEAD_INBOX_KEY are set, so safe to deploy.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server.js

@@ -38,6 +38,31 @@ const MAX_UPLOAD = 5 * 1024 * 1024; /* 5 MB pro eingereichtem Spiel */
 const UPLOAD_DEADLINE = new Date("2026-05-27T22:00:00+02:00");
 const APP_REVISION = process.env.APP_REVISION || "local";
 
+/* Central lead-inbox (infra ADR 012). Sites forward leads here; local files
+   stay as a fallback. Unset env => old local-only behavior. */
+const LEAD_INBOX_URL = process.env.LEAD_INBOX_URL || "";
+const LEAD_INBOX_KEY = process.env.LEAD_INBOX_KEY || "";
+
+async function forwardLeadToInbox(lead) {
+  if (!LEAD_INBOX_URL || !LEAD_INBOX_KEY) return false;
+  try {
+    const res = await fetch(LEAD_INBOX_URL.replace(/\/+$/, "") + "/v1/leads", {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/json",
+        Authorization: "Bearer " + LEAD_INBOX_KEY
+      },
+      /* inbox accepts DE aliases: firma, telefon, nachricht, quelle */
+      body: JSON.stringify(lead),
+      signal: AbortSignal.timeout(5000)
+    });
+    return res.ok;
+  } catch (e) {
+    console.error("[lead] inbox forward failed:", e.message);
+    return false;
+  }
+}
+
 function envFlag(name, defaultValue) {
   const raw = process.env[name];
   if (raw == null || raw === "") return defaultValue;
@@ -227,20 +252,27 @@ function handleLead(req, res) {
       quelle: String(data.quelle || "Landing Page").slice(0, 120)
     };
 
-    try {
-      saveLead(lead);
-    } catch (e) {
-      console.error("[lead] Speichern fehlgeschlagen:", e.message);
-      return sendJSON(res, 500, {
-        error: "Speichern fehlgeschlagen. Bitte später erneut versuchen."
-      });
-    }
+    /* Central inbox is source of truth; local files are the fallback so a
+       lead is never lost if the inbox is unreachable (infra ADR 012). */
+    forwardLeadToInbox(lead).then((forwarded) => {
+      if (!forwarded) {
+        try {
+          saveLead(lead);
+        } catch (e) {
+          console.error("[lead] Speichern fehlgeschlagen:", e.message);
+          return sendJSON(res, 500, {
+            error: "Speichern fehlgeschlagen. Bitte später erneut versuchen."
+          });
+        }
+      }
 
-    console.log(
-      "[lead] " + lead.zeitpunkt + " — " + lead.name +
-      (lead.firma ? " (" + lead.firma + ")" : "") + " <" + lead.email + ">"
-    );
-    sendJSON(res, 200, { ok: true });
+      console.log(
+        "[lead] " + (forwarded ? "→inbox " : "→local ") +
+        lead.zeitpunkt + " — " + lead.name +
+        (lead.firma ? " (" + lead.firma + ")" : "") + " <" + lead.email + ">"
+      );
+      sendJSON(res, 200, { ok: true });
+    });
   });
 }