feat: integrate NextAuth.js for authentication, update database service to use better-sqlite3 adapter, and enhance header component with user session management

src/services/auth.ts

@@ -0,0 +1,68 @@
+import { hash } from 'bcryptjs';
+import { prisma } from '@/services/database';
+
+export interface RegisterInput {
+  email: string;
+  password: string;
+  name?: string;
+}
+
+export interface AuthResult {
+  success: boolean;
+  error?: string;
+  user?: {
+    id: string;
+    email: string;
+    name: string | null;
+  };
+}
+
+export async function registerUser(input: RegisterInput): Promise<AuthResult> {
+  const { email, password, name } = input;
+
+  // Check if user already exists
+  const existingUser = await prisma.user.findUnique({
+    where: { email },
+  });
+
+  if (existingUser) {
+    return {
+      success: false,
+      error: 'Un compte existe déjà avec cet email',
+    };
+  }
+
+  // Hash password
+  const hashedPassword = await hash(password, 12);
+
+  // Create user
+  const user = await prisma.user.create({
+    data: {
+      email,
+      password: hashedPassword,
+      name: name || null,
+    },
+  });
+
+  return {
+    success: true,
+    user: {
+      id: user.id,
+      email: user.email,
+      name: user.name,
+    },
+  };
+}
+
+export async function getUserByEmail(email: string) {
+  return prisma.user.findUnique({
+    where: { email },
+  });
+}
+
+export async function getUserById(id: string) {
+  return prisma.user.findUnique({
+    where: { id },
+  });
+}
+