feat: add new subscription tier and update credit configurations

- Introduced a new "max" subscription tier with associated monthly credits and top-up limits.
- Updated existing subscription tiers' monthly credits and top-up limits for "starter", "pro", and "business".
- Enhanced credit display and overview components to reflect the new tier and its attributes.
- Integrated Polar authentication features for improved subscription management and credit handling.

convex/auth.ts

@@ -1,6 +1,10 @@
 import { createClient, type GenericCtx } from "@convex-dev/better-auth";
 import { convex } from "@convex-dev/better-auth/plugins";
+import { requireRunMutationCtx } from "@convex-dev/better-auth/utils";
+import { checkout, polar, portal, webhooks } from "@polar-sh/better-auth";
+import { Polar } from "@polar-sh/sdk";
 import { components } from "./_generated/api";
+import { internal } from "./_generated/api";
 import { DataModel } from "./_generated/dataModel";
 import { query } from "./_generated/server";
 import { betterAuth } from "better-auth/minimal";
@@ -10,6 +14,11 @@ import authConfig from "./auth.config";
 const siteUrl = process.env.SITE_URL!;
 const appUrl = process.env.APP_URL;
 
+const polarClient = new Polar({
+  accessToken: process.env.POLAR_ACCESS_TOKEN!,
+  server: "production",
+});
+
 // Component Client — stellt Adapter, Helper und Auth-Methoden bereit
 export const authComponent = createClient<DataModel>(components.betterAuth);
 
@@ -68,6 +77,92 @@ export const createAuth = (ctx: GenericCtx<DataModel>) => {
     },
     plugins: [
       convex({ authConfig }),
+      polar({
+        client: polarClient,
+        createCustomerOnSignUp: true,
+        use: [
+          checkout({
+            successUrl: `${siteUrl}/dashboard?checkout=success`,
+            authenticatedUsersOnly: true,
+          }),
+          portal(),
+          webhooks({
+            secret: process.env.POLAR_WEBHOOK_SECRET!,
+            onCustomerStateChanged: async (payload) => {
+              const runMutationCtx = requireRunMutationCtx(ctx);
+              const customerState = payload.data;
+              const userId = customerState.externalId;
+
+              if (!userId) {
+                console.error("Polar customer.state_changed payload without externalId", {
+                  customerId: customerState.id,
+                });
+                return;
+              }
+
+              const subscription = customerState.activeSubscriptions?.[0];
+
+              if (!subscription) {
+                await runMutationCtx.runMutation(internal.polar.handleSubscriptionRevoked, {
+                  userId,
+                });
+                return;
+              }
+
+              const tierMetadata = subscription.metadata.tier;
+              const creditsMetadata = subscription.metadata.credits;
+              const tier = tierMetadata === "starter" || tierMetadata === "pro" || tierMetadata === "max"
+                ? tierMetadata
+                : undefined;
+              const monthlyCredits = Number(creditsMetadata);
+
+              if (!tier || !Number.isFinite(monthlyCredits) || monthlyCredits <= 0) {
+                console.error("Missing or invalid Polar subscription metadata", {
+                  subscriptionId: subscription.id,
+                  tier: tierMetadata,
+                  credits: creditsMetadata,
+                });
+                return;
+              }
+
+              await runMutationCtx.runMutation(internal.polar.handleSubscriptionActivated, {
+                userId,
+                tier,
+                polarSubscriptionId: subscription.id,
+                currentPeriodStart: subscription.currentPeriodStart.getTime(),
+                currentPeriodEnd: subscription.currentPeriodEnd.getTime(),
+                monthlyCredits,
+              });
+            },
+            onOrderPaid: async (payload) => {
+              const runMutationCtx = requireRunMutationCtx(ctx);
+              const order = payload.data;
+              const metadata = order.product?.metadata;
+              const type = metadata?.type;
+              const credits = Number(metadata?.credits);
+
+              if (type !== "topup" || !Number.isFinite(credits) || credits <= 0) {
+                return;
+              }
+
+              const userId = order.customer.externalId;
+              if (!userId) {
+                console.error("Polar order.paid payload without externalId", {
+                  orderId: order.id,
+                });
+                return;
+              }
+
+              await runMutationCtx.runMutation(internal.polar.handleTopUpPaid, {
+                userId,
+                credits,
+                polarOrderId: order.id,
+                amountPaidEuroCents: order.totalAmount,
+              });
+            },
+          }),
+        ],
+      }),
     ],
   });
 };