refactor: replace Loader2 with Spinner component across the application

This update standardizes the loading indicators by replacing all instances of Loader2 with the new Spinner component. The Spinner component provides a consistent look and feel for loading states throughout the UI, enhancing the user experience.

Changes include:
- Updated loading indicators in various components such as popovers, modals, and views.
- Ensured that the Spinner component is used with appropriate sizes for different contexts.

No functional changes were made; this is purely a visual and structural improvement.

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

@@ -5,7 +5,8 @@ import { useAppStore, Feature } from '@/store/app-store';
 import { Card, CardContent } from '@/components/ui/card';
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
-import { Bot, Send, User, Loader2, Sparkles, FileText, ArrowLeft, CheckCircle } from 'lucide-react';
+import { Bot, Send, User, Sparkles, FileText, ArrowLeft, CheckCircle } from 'lucide-react';
+import { Spinner } from '@/components/ui/spinner';
 import { cn, generateUUID } from '@/lib/utils';
 import { getElectronAPI } from '@/lib/electron';
 import { Markdown } from '@/components/ui/markdown';
@@ -491,7 +492,7 @@ export function InterviewView() {
             <Card className="border border-primary/30 bg-card">
               <CardContent className="p-3">
                 <div className="flex items-center gap-2">
-                  <Loader2 className="w-4 h-4 animate-spin text-primary" />
+                  <Spinner size="sm" />
                   <span className="text-sm text-primary">Generating specification...</span>
                 </div>
               </CardContent>
@@ -571,7 +572,7 @@ export function InterviewView() {
                   >
                     {isGenerating ? (
                       <>
-                        <Loader2 className="w-4 h-4 mr-2 animate-spin" />
+                        <Spinner size="sm" className="mr-2" />
                         Creating...
                       </>
                     ) : (