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/lib/schemas/auth.ts

@@ -0,0 +1,39 @@
+import { z } from 'zod'
+
+export const registerSchema = z.object({
+  email: z.string()
+    .email('Email non valida'),
+  password: z.string()
+    .min(8, 'La password deve contenere almeno 8 caratteri')
+    .regex(/[0-9]/, 'La password deve contenere almeno un numero')
+    .regex(/[A-Z]/, 'La password deve contenere almeno una lettera maiuscola'),
+  confirmPassword: z.string()
+}).refine((data) => data.password === data.confirmPassword, {
+  message: 'Le password non coincidono',
+  path: ['confirmPassword'],
+})
+
+export const loginSchema = z.object({
+  email: z.string().email('Email non valida'),
+  password: z.string().min(1, 'Password richiesta'),
+})
+
+export const resetPasswordSchema = z.object({
+  email: z.string().email('Email non valida'),
+})
+
+export const updatePasswordSchema = z.object({
+  password: z.string()
+    .min(8, 'La password deve contenere almeno 8 caratteri')
+    .regex(/[0-9]/, 'La password deve contenere almeno un numero')
+    .regex(/[A-Z]/, 'La password deve contenere almeno una lettera maiuscola'),
+  confirmPassword: z.string()
+}).refine((data) => data.password === data.confirmPassword, {
+  message: 'Le password non coincidono',
+  path: ['confirmPassword'],
+})
+
+export type RegisterInput = z.infer<typeof registerSchema>
+export type LoginInput = z.infer<typeof loginSchema>
+export type ResetPasswordInput = z.infer<typeof resetPasswordSchema>
+export type UpdatePasswordInput = z.infer<typeof updatePasswordSchema>