feat: add user accounts, authentication, and game history with Prisma 7

- Implement user registration and login with NextAuth v5 (email/password, JWT)
- Add authentication modal in UI with login/register tabs
- Create user profile screen showing game statistics and history
- Integrate Prisma 7 ORM with SQLite database for data persistence
- Store game results (mode, path, clicks, time) in database
- Auto-save completed games only when user is authenticated
- Separate business logic into reusable hooks (useSoloGame, useMultiGame)
- Organize UI into composable screen components (HomeScreen, SoloScreen, ProfileScreen, etc)
- Add session persistence across F5 refresh for solo and multiplayer
- Style auth modal, account button, and profile stats dashboard

app/components/AuthModal.tsx

@@ -0,0 +1,102 @@
+"use client";
+
+import { useState } from "react";
+import { signIn } from "next-auth/react";
+
+type Mode = "login" | "register";
+
+export function AuthModal({ onClose, onSuccess }: { onClose: () => void; onSuccess: () => void }) {
+  const [mode, setMode] = useState<Mode>("login");
+  const [name, setName] = useState("");
+  const [email, setEmail] = useState("");
+  const [password, setPassword] = useState("");
+  const [error, setError] = useState<string | null>(null);
+  const [loading, setLoading] = useState(false);
+
+  async function handleSubmit(e: React.FormEvent) {
+    e.preventDefault();
+    setError(null);
+    setLoading(true);
+
+    try {
+      if (mode === "register") {
+        const res = await fetch("/api/register", {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ name, email, password }),
+        });
+        const data = await res.json() as { error?: string };
+        if (!res.ok) { setError(data.error ?? "Erreur"); return; }
+      }
+
+      const result = await signIn("credentials", {
+        email, password, redirect: false,
+      });
+
+      if (result?.error) { setError("Email ou mot de passe incorrect"); return; }
+      onSuccess();
+    } finally {
+      setLoading(false);
+    }
+  }
+
+  return (
+    <div className="modal-overlay" onClick={onClose}>
+      <div className="modal-box" onClick={(e) => e.stopPropagation()}>
+        <div className="modal-tabs">
+          <button
+            className={`modal-tab ${mode === "login" ? "active" : ""}`}
+            onClick={() => { setMode("login"); setError(null); }}
+          >
+            Connexion
+          </button>
+          <button
+            className={`modal-tab ${mode === "register" ? "active" : ""}`}
+            onClick={() => { setMode("register"); setError(null); }}
+          >
+            Inscription
+          </button>
+        </div>
+
+        <form className="modal-form" onSubmit={handleSubmit}>
+          {mode === "register" && (
+            <input
+              className="input"
+              type="text"
+              placeholder="Pseudo"
+              value={name}
+              onChange={(e) => setName(e.target.value)}
+              required
+              maxLength={30}
+            />
+          )}
+          <input
+            className="input"
+            type="email"
+            placeholder="Email"
+            value={email}
+            onChange={(e) => setEmail(e.target.value)}
+            required
+          />
+          <input
+            className="input"
+            type="password"
+            placeholder="Mot de passe"
+            value={password}
+            onChange={(e) => setPassword(e.target.value)}
+            required
+            minLength={6}
+          />
+
+          {error && <div className="error-banner" style={{ marginBottom: 0 }}>{error}</div>}
+
+          <button className="btn btn-primary" type="submit" disabled={loading}>
+            {loading ? "Chargement..." : mode === "login" ? "Se connecter" : "Créer un compte"}
+          </button>
+        </form>
+
+        <button className="modal-close" onClick={onClose} aria-label="Fermer">✕</button>
+      </div>
+    </div>
+  );
+}