Implement session management (Task 5)

- Configure JWT session strategy with 30-day expiration
- Implement session validation middleware for route protection
- Create logout functionality with session termination
- Handle session expiration automatically via JWT
- Add session helper functions (getCurrentSession, isAuthenticated)
- Protect routes: /, /list/*, /profile/*, /invitations/*
- Redirect unauthenticated users to login with callback URL
- Requirements: 2.4, 2.5, 3.1, 3.2, 3.4

lib/auth-actions.ts

@@ -3,7 +3,7 @@
 import { prisma } from './db'
 import bcrypt from 'bcryptjs'
 import { z } from 'zod'
-import { signIn } from '@/auth'
+import { signIn, signOut } from '@/auth'
 
 // Validation schemas
 const registerSchema = z.object({
@@ -132,3 +132,44 @@ export async function loginUser(
     return { success: false, error: 'Invalid email or password' }
   }
 }
+
+/**
+ * Logout user and terminate session
+ * Requirement: 2.5 - Logout terminates session and clears authentication tokens
+ */
+export async function logoutUser(): Promise<void> {
+  try {
+    // Sign out using NextAuth - this will:
+    // 1. Clear the session token
+    // 2. Remove authentication cookies
+    // 3. Terminate the session
+    await signOut({ redirect: false })
+  } catch (error) {
+    console.error('Logout error:', error)
+    throw new Error('Logout failed')
+  }
+}
+
+/**
+ * Get current session
+ * Requirements: 3.2 - Session validation and persistence
+ */
+export async function getCurrentSession() {
+  try {
+    const { auth } = await import('@/auth')
+    const session = await auth()
+    return session
+  } catch (error) {
+    console.error('Session retrieval error:', error)
+    return null
+  }
+}
+
+/**
+ * Validate if user is authenticated
+ * Requirements: 2.4, 3.3 - Session expiration and validation
+ */
+export async function isAuthenticated(): Promise<boolean> {
+  const session = await getCurrentSession()
+  return !!session?.user
+}