refactor: Extract reusable UI components and add TDD documentation

- Add comprehensive TDD documentation to CLAUDE.md with coverage requirements and examples
- Extract reusable UI components to frontend/src/components/ui/ (Modal, FormInput, Button, Alert, etc.)
- Add shared constants (schedulePresets) and utility hooks (useCrudMutation, useFormValidation)
- Update frontend/CLAUDE.md with component documentation and usage examples
- Refactor CreateTaskModal to use shared components and constants
- Fix test assertions to be more robust and accurate across all test files

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

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

frontend/src/components/ui/StepIndicator.tsx

@@ -0,0 +1,118 @@
+import React from 'react';
+import { Check } from 'lucide-react';
+
+interface Step {
+  id: string | number;
+  label: string;
+  description?: string;
+}
+
+interface StepIndicatorProps {
+  steps: Step[];
+  currentStep: number;
+  /** Color for completed/active steps */
+  color?: 'blue' | 'brand' | 'green' | 'purple';
+  /** Show connector lines between steps */
+  showConnectors?: boolean;
+  /** Additional class name */
+  className?: string;
+}
+
+const colorClasses = {
+  blue: {
+    active: 'bg-blue-600 text-white',
+    completed: 'bg-blue-600 text-white',
+    pending: 'bg-gray-200 dark:bg-gray-700 text-gray-500',
+    textActive: 'text-blue-600 dark:text-blue-400',
+    textPending: 'text-gray-400',
+    connector: 'bg-blue-600',
+    connectorPending: 'bg-gray-200 dark:bg-gray-700',
+  },
+  brand: {
+    active: 'bg-brand-600 text-white',
+    completed: 'bg-brand-600 text-white',
+    pending: 'bg-gray-200 dark:bg-gray-700 text-gray-500',
+    textActive: 'text-brand-600 dark:text-brand-400',
+    textPending: 'text-gray-400',
+    connector: 'bg-brand-600',
+    connectorPending: 'bg-gray-200 dark:bg-gray-700',
+  },
+  green: {
+    active: 'bg-green-600 text-white',
+    completed: 'bg-green-600 text-white',
+    pending: 'bg-gray-200 dark:bg-gray-700 text-gray-500',
+    textActive: 'text-green-600 dark:text-green-400',
+    textPending: 'text-gray-400',
+    connector: 'bg-green-600',
+    connectorPending: 'bg-gray-200 dark:bg-gray-700',
+  },
+  purple: {
+    active: 'bg-purple-600 text-white',
+    completed: 'bg-purple-600 text-white',
+    pending: 'bg-gray-200 dark:bg-gray-700 text-gray-500',
+    textActive: 'text-purple-600 dark:text-purple-400',
+    textPending: 'text-gray-400',
+    connector: 'bg-purple-600',
+    connectorPending: 'bg-gray-200 dark:bg-gray-700',
+  },
+};
+
+export const StepIndicator: React.FC<StepIndicatorProps> = ({
+  steps,
+  currentStep,
+  color = 'blue',
+  showConnectors = true,
+  className = '',
+}) => {
+  const colors = colorClasses[color];
+
+  return (
+    <div className={`flex items-center justify-center ${className}`}>
+      {steps.map((step, index) => {
+        const stepNumber = index + 1;
+        const isCompleted = stepNumber < currentStep;
+        const isActive = stepNumber === currentStep;
+        const isPending = stepNumber > currentStep;
+
+        return (
+          <React.Fragment key={step.id}>
+            <div className="flex items-center gap-2">
+              {/* Step circle */}
+              <div
+                className={`w-8 h-8 rounded-full flex items-center justify-center font-medium text-sm transition-colors ${
+                  isCompleted
+                    ? colors.completed
+                    : isActive
+                    ? colors.active
+                    : colors.pending
+                }`}
+              >
+                {isCompleted ? <Check size={16} /> : stepNumber}
+              </div>
+
+              {/* Step label */}
+              <span
+                className={`font-medium text-sm ${
+                  isActive || isCompleted ? colors.textActive : colors.textPending
+                }`}
+              >
+                {step.label}
+              </span>
+            </div>
+
+            {/* Connector */}
+            {showConnectors && index < steps.length - 1 && (
+              <div
+                className={`w-16 h-0.5 mx-4 ${
+                  stepNumber < currentStep ? colors.connector : colors.connectorPending
+                }`}
+              />
+            )}
+          </React.Fragment>
+        );
+      })}
+    </div>
+  );
+};
+
+export default StepIndicator;