feat(01-06): create password update page with validation

- Implemented UpdatePasswordPage with password strength indicator
- Added password validation utility with comprehensive checks
- Enhanced AuthProvider with updatePasswordFromReset method
- Extended AuthRepository interface and implementation for password reset
- Added InvalidTokenException to auth exception hierarchy
- Includes accessibility features and error handling
- Password strength indicator with real-time feedback

Files:
- lib/features/authentication/presentation/pages/update_password_page.dart
- lib/core/utils/password_validator.dart
- lib/providers/auth_provider.dart
- lib/features/authentication/domain/repositories/auth_repository.dart
- lib/features/authentication/data/repositories/auth_repository_impl.dart
- lib/core/errors/auth_exceptions.dart

lib/core/errors/auth_exceptions.dart

@@ -120,6 +120,19 @@ class EmailNotVerifiedException extends AuthException {
         );
 }
 
+/// Exception thrown when a reset token is invalid or expired
+class InvalidTokenException extends AuthException {
+  const InvalidTokenException({
+    String message = 'Reset token is invalid or has expired',
+    String? code,
+    dynamic originalError,
+  }) : super(
+          message: message,
+          code: code ?? 'INVALID_TOKEN',
+          originalError: originalError,
+        );
+}
+
 /// Exception thrown when too many login attempts are made
 class TooManyRequestsException extends AuthException {
   const TooManyRequestsException({
@@ -198,6 +211,17 @@ class AuthExceptionFactory {
       );
     }
     
+    if (lowerMessage.contains('invalid token') ||
+        lowerMessage.contains('token expired') ||
+        lowerMessage.contains('reset token') ||
+        lowerMessage.contains('session has expired')) {
+      return InvalidTokenException(
+        message: _extractUserFriendlyMessage(errorMessage) ?? 'Reset token is invalid or has expired',
+        code: errorCode,
+        originalError: error,
+      );
+    }
+    
     if (lowerMessage.contains('user not found') ||
         lowerMessage.contains('no user found') ||
         lowerMessage.contains('user does not exist')) {

lib/core/utils/password_validator.dart

@@ -0,0 +1,92 @@
+/// Utility class for password validation and strength checking
+class PasswordValidator {
+  /// Minimum password length
+  static const int minLength = 8;
+  
+  /// Validates a password against security requirements
+  /// 
+  /// Returns [PasswordValidationResult] with detailed validation information
+  static PasswordValidationResult validate(String password) {
+    final errors = <String>[];
+    double strength = 0.0;
+    
+    // Check length
+    if (password.length < minLength) {
+      errors.add('Password must be at least $minLength characters');
+    } else {
+      strength += 0.25;
+    }
+    
+    // Check for uppercase letter
+    if (!password.contains(RegExp(r'[A-Z]'))) {
+      errors.add('Password must contain at least one uppercase letter');
+    } else {
+      strength += 0.25;
+    }
+    
+    // Check for lowercase letter
+    if (!password.contains(RegExp(r'[a-z]'))) {
+      errors.add('Password must contain at least one lowercase letter');
+    } else {
+      strength += 0.25;
+    }
+    
+    // Check for number
+    if (!password.contains(RegExp(r'[0-9]'))) {
+      errors.add('Password must contain at least one number');
+    } else {
+      strength += 0.25;
+    }
+    
+    // Bonus points for special characters
+    if (password.contains(RegExp(r'[!@#$%^&*(),.?":{}|<>]'))) {
+      strength = (strength + 0.1).clamp(0.0, 1.0);
+    }
+    
+    // Bonus points for longer passwords
+    if (password.length >= 12) {
+      strength = (strength + 0.1).clamp(0.0, 1.0);
+    }
+    
+    return PasswordValidationResult(
+      isValid: errors.isEmpty,
+      errors: errors,
+      strength: strength,
+    );
+  }
+  
+  /// Gets password strength text based on strength value
+  static String getStrengthText(double strength) {
+    if (strength <= 0.25) return 'Weak';
+    if (strength <= 0.5) return 'Fair';
+    if (strength <= 0.75) return 'Good';
+    return 'Strong';
+  }
+  
+  /// Gets password strength color based on strength value
+  static String getStrengthColor(double strength) {
+    if (strength <= 0.25) return 'red';
+    if (strength <= 0.5) return 'orange';
+    if (strength <= 0.75) return 'yellow';
+    return 'green';
+  }
+}
+
+/// Result of password validation
+class PasswordValidationResult {
+  final bool isValid;
+  final List<String> errors;
+  final double strength;
+  
+  const PasswordValidationResult({
+    required this.isValid,
+    required this.errors,
+    required this.strength,
+  });
+  
+  /// Gets the strength text for this result
+  String get strengthText => PasswordValidator.getStrengthText(strength);
+  
+  /// Gets the strength color name for this result
+  String get strengthColor => PasswordValidator.getStrengthColor(strength);
+}