init: kovakemlak-crm project scaffold

- Next.js 16 + Appwrite multi-tenant emlak CRM
- Database: kovakemlak-db (properties, customers, customer_searches, property_matches, presentations, investors, activities, tenant_settings)
- Same stack as isletmem-kovakcrm (shadcn/ui template base)
- Modules: portföy, müşteri takibi, arama kriterleri, otomatik eşleştirme, sunum linki, yatırımcı portalı

src/lib/payments/polar.ts

@@ -0,0 +1,63 @@
+import "server-only";
+
+import { validateEvent, WebhookVerificationError } from "@polar-sh/sdk/webhooks";
+
+const POLAR_API_BASE = "https://api.polar.sh";
+const ACCESS_TOKEN = process.env.POLAR_ACCESS_TOKEN ?? "";
+const WEBHOOK_SECRET = process.env.POLAR_WEBHOOK_SECRET ?? "";
+
+export const POLAR_PRODUCT_ID = process.env.POLAR_PRODUCT_ID ?? "";
+
+export function isPolarEnabled(): boolean {
+  return (
+    process.env.PAYMENT_PROVIDER === "polar" &&
+    Boolean(ACCESS_TOKEN) &&
+    Boolean(POLAR_PRODUCT_ID)
+  );
+}
+
+export type PolarCheckout = {
+  id: string;
+  url: string;
+};
+
+export async function createPolarCheckout(params: {
+  orderId: string;
+  tenantId: string;
+  userEmail: string;
+  successUrl: string;
+}): Promise<PolarCheckout> {
+  const res = await fetch(`${POLAR_API_BASE}/v1/checkouts/`, {
+    method: "POST",
+    headers: {
+      Authorization: `Bearer ${ACCESS_TOKEN}`,
+      "Content-Type": "application/json",
+    },
+    body: JSON.stringify({
+      products: [POLAR_PRODUCT_ID],
+      customer_email: params.userEmail,
+      success_url: params.successUrl,
+      return_url: params.successUrl,
+      metadata: {
+        crm_order_id: params.orderId,
+        tenant_id: params.tenantId,
+      },
+    }),
+  });
+
+  if (!res.ok) {
+    const text = await res.text();
+    throw new Error(`Polar checkout oluşturulamadı: ${text}`);
+  }
+
+  return res.json() as Promise<PolarCheckout>;
+}
+
+// Polar resmi SDK ile webhook doğrulama ve parse
+// Hata fırlatırsa imza geçersiz demektir
+export function verifyAndParsePolarWebhook(
+  headers: Record<string, string>,
+  rawBody: string,
+): ReturnType<typeof validateEvent> {
+  return validateEvent(rawBody, headers, WEBHOOK_SECRET);
+}