refactor: extract Enhance with AI into shared components

Extract all "Enhance with AI" functionality into reusable shared components
following DRY principles and clean code guidelines.

Changes:
- Create shared/enhancement/ folder for related functionality
- Extract EnhanceWithAI component (AI enhancement with model override)
- Extract EnhancementHistoryButton component (version history UI)
- Extract enhancement constants and types
- Refactor add-feature-dialog.tsx to use shared components
- Refactor edit-feature-dialog.tsx to use shared components
- Refactor follow-up-dialog.tsx to use shared components
- Add history tracking to add-feature-dialog for consistency

Benefits:
- Eliminated ~527 lines of duplicated code
- Single source of truth for enhancement logic
- Consistent UX across all dialogs
- Easier maintenance and extensibility
- Better code organization

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

apps/ui/src/components/views/board-view.tsx

@@ -161,12 +161,14 @@ export function BoardView() {
     followUpPrompt,
     followUpImagePaths,
     followUpPreviewMap,
+    followUpPromptHistory,
     setShowFollowUpDialog,
     setFollowUpFeature,
     setFollowUpPrompt,
     setFollowUpImagePaths,
     setFollowUpPreviewMap,
     handleFollowUpDialogChange,
+    addToPromptHistory,
   } = useFollowUpState();
 
   // Selection mode hook for mass editing
@@ -1422,6 +1424,8 @@ export function BoardView() {
         onPreviewMapChange={setFollowUpPreviewMap}
         onSend={handleSendFollowUp}
         isMaximized={isMaximized}
+        promptHistory={followUpPromptHistory}
+        onHistoryAdd={addToPromptHistory}
       />
 
       {/* Backlog Plan Dialog */}