feat(01-03): add validation schemas and server actions

- Add Zod validation schemas for auth operations
- Add server actions for register, login, reset, update password
- Add clsx and tailwind-merge for class utilities
- Password validation: 8+ chars, 1 number, 1 uppercase
- Error messages in Italian per user requirement
- Specific error messages (not generic 'invalid credentials')

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/actions/auth.ts

@@ -0,0 +1,164 @@
+'use server'
+
+import { createClient } from '@/lib/supabase/server'
+import { registerSchema, loginSchema, resetPasswordSchema, updatePasswordSchema } from '@/lib/schemas/auth'
+import { redirect } from 'next/navigation'
+import { revalidatePath } from 'next/cache'
+
+export type ActionState = {
+  error?: string
+  fieldErrors?: Record<string, string[]>
+  success?: boolean
+  message?: string
+}
+
+export async function registerUser(
+  prevState: ActionState,
+  formData: FormData
+): Promise<ActionState> {
+  const supabase = await createClient()
+
+  const parsed = registerSchema.safeParse({
+    email: formData.get('email'),
+    password: formData.get('password'),
+    confirmPassword: formData.get('confirmPassword'),
+  })
+
+  if (!parsed.success) {
+    return {
+      fieldErrors: parsed.error.flatten().fieldErrors,
+    }
+  }
+
+  const { data, error } = await supabase.auth.signUp({
+    email: parsed.data.email,
+    password: parsed.data.password,
+    options: {
+      emailRedirectTo: `${process.env.NEXT_PUBLIC_APP_URL}/auth/callback`,
+    }
+  })
+
+  if (error) {
+    // SPECIFIC error messages per user requirement
+    if (error.message.includes('already registered')) {
+      return { error: 'Questa email e gia registrata' }
+    }
+    if (error.message.includes('invalid')) {
+      return { error: 'Email non valida' }
+    }
+    return { error: error.message }
+  }
+
+  return {
+    success: true,
+    message: 'Registrazione completata! Controlla la tua email per confermare l\'account.'
+  }
+}
+
+export async function loginUser(
+  prevState: ActionState,
+  formData: FormData
+): Promise<ActionState> {
+  const supabase = await createClient()
+
+  const parsed = loginSchema.safeParse({
+    email: formData.get('email'),
+    password: formData.get('password'),
+  })
+
+  if (!parsed.success) {
+    return {
+      fieldErrors: parsed.error.flatten().fieldErrors,
+    }
+  }
+
+  const { data, error } = await supabase.auth.signInWithPassword({
+    email: parsed.data.email,
+    password: parsed.data.password,
+  })
+
+  if (error) {
+    // SPECIFIC error messages per user requirement
+    if (error.message.includes('Invalid login credentials')) {
+      return { error: 'Email o password errata' }
+    }
+    if (error.message.includes('Email not confirmed')) {
+      return { error: 'Devi confermare la tua email prima di accedere' }
+    }
+    return { error: error.message }
+  }
+
+  revalidatePath('/', 'layout')
+  redirect('/dashboard')
+}
+
+export async function resetPassword(
+  prevState: ActionState,
+  formData: FormData
+): Promise<ActionState> {
+  const supabase = await createClient()
+
+  const parsed = resetPasswordSchema.safeParse({
+    email: formData.get('email'),
+  })
+
+  if (!parsed.success) {
+    return {
+      fieldErrors: parsed.error.flatten().fieldErrors,
+    }
+  }
+
+  const { error } = await supabase.auth.resetPasswordForEmail(
+    parsed.data.email,
+    {
+      redirectTo: `${process.env.NEXT_PUBLIC_APP_URL}/auth/callback?next=/update-password`,
+    }
+  )
+
+  if (error) {
+    return { error: error.message }
+  }
+
+  return {
+    success: true,
+    message: 'Se l\'email esiste, riceverai un link per reimpostare la password.'
+  }
+}
+
+export async function updatePassword(
+  prevState: ActionState,
+  formData: FormData
+): Promise<ActionState> {
+  const supabase = await createClient()
+
+  const parsed = updatePasswordSchema.safeParse({
+    password: formData.get('password'),
+    confirmPassword: formData.get('confirmPassword'),
+  })
+
+  if (!parsed.success) {
+    return {
+      fieldErrors: parsed.error.flatten().fieldErrors,
+    }
+  }
+
+  const { error } = await supabase.auth.updateUser({
+    password: parsed.data.password,
+  })
+
+  if (error) {
+    return { error: error.message }
+  }
+
+  return {
+    success: true,
+    message: 'Password aggiornata con successo!'
+  }
+}
+
+export async function signOut() {
+  const supabase = await createClient()
+  await supabase.auth.signOut()
+  revalidatePath('/', 'layout')
+  redirect('/login')
+}