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- Removed outdated Canvas Implementation Guide documentation.

app/(app)/canvas/[canvasId]/page.tsx

@@ -1,9 +1,10 @@
-import { redirect } from "next/navigation";
+import { notFound, redirect } from "next/navigation";
 
 import Canvas from "@/components/canvas/canvas";
 import CanvasToolbar from "@/components/canvas/canvas-toolbar";
+import { api } from "@/convex/_generated/api";
 import type { Id } from "@/convex/_generated/dataModel";
-import { isAuthenticated } from "@/lib/auth-server";
+import { fetchAuthQuery, isAuthenticated } from "@/lib/auth-server";
 
 export default async function CanvasPage({
   params,
@@ -18,6 +19,17 @@ export default async function CanvasPage({
   const { canvasId } = await params;
   const typedCanvasId = canvasId as Id<"canvases">;
 
+  try {
+    const canvas = await fetchAuthQuery(api.canvases.get, {
+      canvasId: typedCanvasId,
+    });
+    if (!canvas) {
+      notFound();
+    }
+  } catch {
+    notFound();
+  }
+
   return (
     <div className="relative h-screen w-screen overflow-hidden">
       <CanvasToolbar canvasId={typedCanvasId} />

app/auth/sign-in/page.tsx

@@ -0,0 +1,101 @@
+"use client";
+
+import { useState } from "react";
+import { authClient } from "@/lib/auth-client";
+import { useRouter } from "next/navigation";
+import Link from "next/link";
+
+export default function SignInPage() {
+  const router = useRouter();
+  const [email, setEmail] = useState("");
+  const [password, setPassword] = useState("");
+  const [error, setError] = useState("");
+  const [loading, setLoading] = useState(false);
+
+  const handleSignIn = async (e: React.FormEvent) => {
+    e.preventDefault();
+    setError("");
+    setLoading(true);
+
+    try {
+      const result = await authClient.signIn.email({
+        email,
+        password,
+      });
+
+      if (result.error) {
+        setError(result.error.message ?? "Anmeldung fehlgeschlagen");
+      } else {
+        router.push("/dashboard");
+      }
+    } catch {
+      setError("Ein unerwarteter Fehler ist aufgetreten");
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <div className="flex min-h-screen items-center justify-center bg-background">
+      <div className="w-full max-w-sm space-y-6 rounded-xl border bg-card p-8 shadow-sm">
+        <div className="text-center">
+          <h1 className="text-2xl font-semibold">Willkommen zurück 🍋</h1>
+          <p className="mt-1 text-sm text-muted-foreground">
+            Melde dich bei LemonSpace an
+          </p>
+        </div>
+
+        <form onSubmit={handleSignIn} className="space-y-4">
+          <div>
+            <label htmlFor="email" className="block text-sm font-medium mb-1.5">
+              E-Mail
+            </label>
+            <input
+              id="email"
+              type="email"
+              value={email}
+              onChange={(e) => setEmail(e.target.value)}
+              required
+              className="w-full rounded-lg border bg-background px-3 py-2 text-sm outline-none focus:ring-2 focus:ring-primary"
+              placeholder="name@beispiel.de"
+            />
+          </div>
+
+          <div>
+            <label htmlFor="password" className="block text-sm font-medium mb-1.5">
+              Passwort
+            </label>
+            <input
+              id="password"
+              type="password"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              required
+              className="w-full rounded-lg border bg-background px-3 py-2 text-sm outline-none focus:ring-2 focus:ring-primary"
+              placeholder="Dein Passwort"
+            />
+          </div>
+
+          {error && (
+            <p className="text-sm text-red-500">{error}</p>
+          )}
+
+          <button
+            type="submit"
+            disabled={loading}
+            className="w-full rounded-lg bg-primary px-4 py-2.5 text-sm font-medium text-primary-foreground hover:bg-primary/90 disabled:opacity-50 transition-colors"
+          >
+            {loading ? "Wird angemeldet…" : "Anmelden"}
+          </button>
+        </form>
+
+        <p className="text-center text-sm text-muted-foreground">
+          Noch kein Konto?{" "}
+          <Link href="/auth/sign-up" className="font-medium text-primary hover:underline">
+            Registrieren
+          </Link>
+        </p>
+      </div>
+    </div>
+  );
+}

app/auth/sign-up/page.tsx

@@ -0,0 +1,143 @@
+"use client";
+
+import { useState } from "react";
+import { authClient } from "@/lib/auth-client";
+import { useRouter } from "next/navigation";
+import Link from "next/link";
+
+export default function SignUpPage() {
+  const router = useRouter();
+  const [name, setName] = useState("");
+  const [email, setEmail] = useState("");
+  const [password, setPassword] = useState("");
+  const [error, setError] = useState("");
+  const [success, setSuccess] = useState(false);
+  const [loading, setLoading] = useState(false);
+
+  const handleSignUp = async (e: React.FormEvent) => {
+    e.preventDefault();
+    setError("");
+    setLoading(true);
+
+    try {
+      const result = await authClient.signUp.email({
+        email,
+        password,
+        name,
+      });
+
+      if (result.error) {
+        setError(result.error.message ?? "Registrierung fehlgeschlagen");
+      } else {
+        setSuccess(true);
+      }
+    } catch {
+      setError("Ein unerwarteter Fehler ist aufgetreten");
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  if (success) {
+    return (
+      <div className="flex min-h-screen items-center justify-center bg-background">
+        <div className="w-full max-w-sm space-y-4 rounded-xl border bg-card p-8 shadow-sm">
+          <div className="text-center">
+            <div className="text-4xl mb-3">📧</div>
+            <h1 className="text-xl font-semibold">E-Mail bestätigen</h1>
+            <p className="mt-2 text-sm text-muted-foreground">
+              Wir haben dir eine E-Mail an <strong>{email}</strong> geschickt.
+              Klicke auf den Link, um dein Konto zu aktivieren.
+            </p>
+          </div>
+          <button
+            onClick={() => router.push("/auth/sign-in")}
+            className="w-full rounded-lg bg-primary px-4 py-2.5 text-sm font-medium text-primary-foreground hover:bg-primary/90 transition-colors"
+          >
+            Zum Login
+          </button>
+        </div>
+      </div>
+    );
+  }
+
+  return (
+    <div className="flex min-h-screen items-center justify-center bg-background">
+      <div className="w-full max-w-sm space-y-6 rounded-xl border bg-card p-8 shadow-sm">
+        <div className="text-center">
+          <h1 className="text-2xl font-semibold">Konto erstellen 🍋</h1>
+          <p className="mt-1 text-sm text-muted-foreground">
+            Erstelle dein LemonSpace-Konto
+          </p>
+        </div>
+
+        <form onSubmit={handleSignUp} className="space-y-4">
+          <div>
+            <label htmlFor="name" className="block text-sm font-medium mb-1.5">
+              Name
+            </label>
+            <input
+              id="name"
+              type="text"
+              value={name}
+              onChange={(e) => setName(e.target.value)}
+              required
+              className="w-full rounded-lg border bg-background px-3 py-2 text-sm outline-none focus:ring-2 focus:ring-primary"
+              placeholder="Dein Name"
+            />
+          </div>
+
+          <div>
+            <label htmlFor="email" className="block text-sm font-medium mb-1.5">
+              E-Mail
+            </label>
+            <input
+              id="email"
+              type="email"
+              value={email}
+              onChange={(e) => setEmail(e.target.value)}
+              required
+              className="w-full rounded-lg border bg-background px-3 py-2 text-sm outline-none focus:ring-2 focus:ring-primary"
+              placeholder="name@beispiel.de"
+            />
+          </div>
+
+          <div>
+            <label htmlFor="password" className="block text-sm font-medium mb-1.5">
+              Passwort
+            </label>
+            <input
+              id="password"
+              type="password"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              required
+              minLength={8}
+              className="w-full rounded-lg border bg-background px-3 py-2 text-sm outline-none focus:ring-2 focus:ring-primary"
+              placeholder="Mindestens 8 Zeichen"
+            />
+          </div>
+
+          {error && (
+            <p className="text-sm text-red-500">{error}</p>
+          )}
+
+          <button
+            type="submit"
+            disabled={loading}
+            className="w-full rounded-lg bg-primary px-4 py-2.5 text-sm font-medium text-primary-foreground hover:bg-primary/90 disabled:opacity-50 transition-colors"
+          >
+            {loading ? "Wird erstellt…" : "Konto erstellen"}
+          </button>
+        </form>
+
+        <p className="text-center text-sm text-muted-foreground">
+          Bereits ein Konto?{" "}
+          <Link href="/auth/sign-in" className="font-medium text-primary hover:underline">
+            Anmelden
+          </Link>
+        </p>
+      </div>
+    </div>
+  );
+}

app/page.tsx

@@ -1,10 +1,12 @@
 "use client";
 
 import { authClient } from "@/lib/auth-client";
+import { useRouter } from "next/navigation";
 import Link from "next/link";
 
 export default function Home() {
   const { data: session, isPending } = authClient.useSession();
+  const router = useRouter();
 
   if (isPending) {
     return (
@@ -29,6 +31,12 @@ export default function Home() {
           >
             Zum Dashboard
           </Link>
+          <button
+            onClick={() => authClient.signOut().then(() => router.refresh())}
+            className="rounded-lg border border-border px-6 py-3 text-sm hover:bg-accent"
+          >
+            Abmelden
+          </button>
         </div>
       ) : (
         <div className="flex gap-4">