feat: add Resend integration for email verification and update package dependencies

- Integrated Resend for sending email verification upon user sign-up.
- Updated package.json to include Resend as a dependency.
- Enhanced authentication flow with error handling for email sending.
- Removed outdated Canvas Implementation Guide documentation.

convex/auth.ts

@@ -4,9 +4,11 @@ import { components } from "./_generated/api";
 import { DataModel } from "./_generated/dataModel";
 import { query } from "./_generated/server";
 import { betterAuth } from "better-auth/minimal";
+import { Resend } from "resend";
 import authConfig from "./auth.config";
 
 const siteUrl = process.env.SITE_URL!;
+const appUrl = process.env.APP_URL;
 
 // Component Client — stellt Adapter, Helper und Auth-Methoden bereit
 export const authComponent = createClient<DataModel>(components.betterAuth);
@@ -15,11 +17,54 @@ export const authComponent = createClient<DataModel>(components.betterAuth);
 export const createAuth = (ctx: GenericCtx<DataModel>) => {
   return betterAuth({
     baseURL: siteUrl,
-    trustedOrigins: [siteUrl],
+    trustedOrigins: [siteUrl, "http://localhost:3000"],
     database: authComponent.adapter(ctx),
     emailAndPassword: {
       enabled: true,
-      requireEmailVerification: false, // Später auf true → useSend Integration
+      requireEmailVerification: true,
+      minPasswordLength: 8,
+    },
+    emailVerification: {
+      sendOnSignUp: true,
+      sendVerificationEmail: async ({ user, url }) => {
+        const verificationUrl = new URL(url);
+
+        if (appUrl) {
+          verificationUrl.searchParams.set("callbackURL", `${appUrl}/dashboard`);
+        }
+
+        const apiKey = process.env.RESEND_API_KEY;
+        if (!apiKey) {
+          console.error("RESEND_API_KEY is not set — skipping verification email");
+          return;
+        }
+
+        const resend = new Resend(apiKey);
+        const { error } = await resend.emails.send({
+          from: "LemonSpace <noreply@lemonspace.io>",
+          to: user.email,
+          subject: "Bestätige deine E-Mail-Adresse",
+          html: `
+            <div style="font-family: sans-serif; max-width: 480px; margin: 0 auto;">
+              <h2>Willkommen bei LemonSpace 🍋</h2>
+              <p>Hi ${user.name || ""},</p>
+              <p>Klicke auf den Button, um deine E-Mail-Adresse zu bestätigen:</p>
+              <a href="${verificationUrl.toString()}"
+                 style="display: inline-block; background: #facc15; color: #1a1a1a; padding: 12px 24px; border-radius: 8px; text-decoration: none; font-weight: 600; margin: 16px 0;">
+                E-Mail bestätigen
+              </a>
+              <p style="color: #666; font-size: 13px;">
+                Falls der Button nicht funktioniert, kopiere diesen Link:<br/>
+                <a href="${verificationUrl.toString()}">${verificationUrl.toString()}</a>
+              </p>
+            </div>
+          `,
+        });
+
+        if (error) {
+          console.error("Failed to send verification email:", error);
+        }
+      },
     },
     plugins: [
       convex({ authConfig }),
@@ -31,6 +76,17 @@ export const createAuth = (ctx: GenericCtx<DataModel>) => {
 export const getCurrentUser = query({
   args: {},
   handler: async (ctx) => {
-    return authComponent.safeGetAuthUser(ctx);
+    return authComponent.getAuthUser(ctx);
+  },
+});
+
+export const safeGetAuthUser = query({
+  args: {},
+  handler: async (ctx) => {
+    try {
+      return await authComponent.getAuthUser(ctx);
+    } catch {
+      return null;
+    }
   },
 });