fix: address PR review feedback from Gemini Code Assist

Address three issues identified in code review:

1. Fix missing thinkingLevel parameter (Critical)
   - Added thinkingLevel parameter to enhance API call
   - Updated electron.ts type definition to match http-api-client
   - Fixes functional regression in Claude model enhancement

2. Refactor dropdown menu to use constants dynamically
   - Changed hardcoded DropdownMenuItem components to dynamic generation
   - Now iterates over ENHANCEMENT_MODE_LABELS object
   - Ensures automatic sync when new modes are added
   - Eliminates manual UI updates for new enhancement modes

3. Optimize array reversal performance
   - Added useMemo hook to memoize reversed history array
   - Prevents creating new array on every render
   - Improves performance with lengthy histories

All TypeScript errors resolved. Build verified.

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

apps/ui/src/lib/electron.ts

@@ -612,7 +612,8 @@ export interface ElectronAPI {
     enhance: (
       originalText: string,
       enhancementMode: string,
-      model?: string
+      model?: string,
+      thinkingLevel?: string
     ) => Promise<{
       success: boolean;
       enhancedText?: string;