feat(01-02): configure NextAuth.js v4 with credentials provider and JWT

- Install next-auth@4, bcryptjs, @types/bcryptjs, @types/jest
- src/types/next-auth.d.ts: extend Session/JWT with tenantId, roles, isSuperAdmin
- src/lib/auth-options.ts: CredentialsProvider + JWT/session callbacks, 24h maxAge
- src/lib/auth.ts: getServerSession() and getCurrentUser() server helpers
- src/app/api/auth/[...nextauth]/route.ts: NextAuth GET/POST handler
- src/middleware.ts: withAuth middleware protecting all routes except /login /signup /api/auth/*

src/lib/auth-options.ts

@@ -0,0 +1,100 @@
+import { NextAuthOptions } from "next-auth";
+import CredentialsProvider from "next-auth/providers/credentials";
+import bcrypt from "bcryptjs";
+import { prisma } from "@/lib/prisma";
+import { TenantStatus } from "@prisma/client";
+
+export const authOptions: NextAuthOptions = {
+  session: {
+    strategy: "jwt",
+    maxAge: 24 * 60 * 60, // 24 hours
+  },
+  pages: {
+    signIn: "/login",
+  },
+  providers: [
+    CredentialsProvider({
+      name: "credentials",
+      credentials: {
+        email: { label: "Email", type: "email" },
+        password: { label: "Password", type: "password" },
+      },
+      async authorize(credentials) {
+        if (!credentials?.email || !credentials?.password) {
+          return null;
+        }
+
+        const user = await prisma.user.findFirst({
+          where: {
+            email: credentials.email,
+            isActive: true,
+            OR: [
+              { isSuperAdmin: true },
+              {
+                tenant: {
+                  status: TenantStatus.ACTIVE,
+                },
+              },
+            ],
+          },
+          include: {
+            tenant: {
+              select: { status: true },
+            },
+          },
+        });
+
+        if (!user) {
+          return null;
+        }
+
+        const passwordValid = await bcrypt.compare(
+          credentials.password,
+          user.passwordHash
+        );
+
+        if (!passwordValid) {
+          return null;
+        }
+
+        return {
+          id: user.id,
+          email: user.email,
+          tenantId: user.tenantId,
+          roles: user.roles,
+          isSuperAdmin: user.isSuperAdmin,
+          firstName: user.firstName,
+          lastName: user.lastName,
+        };
+      },
+    }),
+  ],
+  callbacks: {
+    async jwt({ token, user }) {
+      // On initial sign-in, user is populated — persist fields into token
+      if (user) {
+        token.id = user.id;
+        token.email = user.email;
+        token.tenantId = user.tenantId;
+        token.roles = user.roles;
+        token.isSuperAdmin = user.isSuperAdmin;
+        token.firstName = user.firstName;
+        token.lastName = user.lastName;
+      }
+      return token;
+    },
+    async session({ session, token }) {
+      // Expose token fields on session.user for client-side access
+      session.user = {
+        id: token.id,
+        email: token.email,
+        tenantId: token.tenantId,
+        roles: token.roles,
+        isSuperAdmin: token.isSuperAdmin,
+        firstName: token.firstName,
+        lastName: token.lastName,
+      };
+      return session;
+    },
+  },
+};

src/lib/auth.ts

@@ -0,0 +1,26 @@
+import { getServerSession as nextAuthGetServerSession } from "next-auth";
+import { authOptions } from "@/lib/auth-options";
+
+/**
+ * Server-side helper to get the current session.
+ * Wraps next-auth's getServerSession with the app's authOptions.
+ *
+ * Usage (in Server Components, Route Handlers, Server Actions):
+ *   const session = await getServerSession();
+ */
+export async function getServerSession() {
+  return nextAuthGetServerSession(authOptions);
+}
+
+/**
+ * Returns the typed session user or null if not authenticated.
+ * Convenience wrapper that extracts session.user.
+ *
+ * Usage:
+ *   const user = await getCurrentUser();
+ *   if (!user) redirect("/login");
+ */
+export async function getCurrentUser() {
+  const session = await getServerSession();
+  return session?.user ?? null;
+}