feat: enhance authentication UX with password visibility toggle and better error messages

Added comprehensive improvements to the login and authentication flow:

**UI Improvements:**
- Add password visibility toggle (Eye/EyeOff icons) for password fields
- Improve error message consistency with Dutch translations
- Fix syntax error in login page try-catch block

**Error Handling:**
- Add user-friendly error messages for invalid credentials
- Add specific error codes: invalid_credentials, email_not_confirmed
- Improve error message for non-existent accounts during login
- Handle duplicate email detection during signup with auto-switch to login mode

**Middleware:**
- Add /reset-password and /update-password to public routes
- Fix redirect issue preventing access to password reset flow

**Password Reset Flow:**
- Verify password reset works for magic link users (can set initial password)
- Ensure existing password users can reset their password
- Both flows use the same update mechanism via Supabase

**Documentation:**
- Add comprehensive release notes in docs/RELEASE_AUTH_IMPROVEMENTS.md

All changes maintain backward compatibility with existing magic link users.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

lib/auth/client.ts

@@ -158,7 +158,29 @@ export async function loginWithPassword(email: string, password: string) {
     password
   })
 
-  if (error) throw error
+  if (error) {
+    // Provide user-friendly error messages
+    const errorMessage = error.message?.toLowerCase() || ''
+
+    // Invalid login credentials (account doesn't exist OR wrong password)
+    if (errorMessage.includes('invalid login credentials') ||
+        errorMessage.includes('invalid credentials') ||
+        error.status === 400) {
+      const friendlyError = new Error('Email of wachtwoord is onjuist. Controleer je gegevens en probeer opnieuw.')
+      ;(friendlyError as any).code = 'invalid_credentials'
+      throw friendlyError
+    }
+
+    // Email not confirmed
+    if (errorMessage.includes('email not confirmed')) {
+      const friendlyError = new Error('Je email is nog niet geverifieerd. Check je inbox voor de verificatie link.')
+      ;(friendlyError as any).code = 'email_not_confirmed'
+      throw friendlyError
+    }
+
+    // Generic error fallback
+    throw error
+  }
 
   return {
     success: true,