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/dialogs/board-background-modal.tsx

@@ -1,6 +1,7 @@
 import { useState, useRef, useCallback, useEffect } from 'react';
 import { createLogger } from '@automaker/utils/logger';
-import { ImageIcon, Upload, Loader2, Trash2 } from 'lucide-react';
+import { ImageIcon, Upload, Trash2 } from 'lucide-react';
+import { Spinner } from '@/components/ui/spinner';
 
 const logger = createLogger('BoardBackgroundModal');
 import {
@@ -313,7 +314,7 @@ export function BoardBackgroundModal({ open, onOpenChange }: BoardBackgroundModa
                     />
                     {isProcessing && (
                       <div className="absolute inset-0 flex items-center justify-center bg-background/80">
-                        <Loader2 className="w-6 h-6 animate-spin text-brand-500" />
+                        <Spinner size="lg" />
                       </div>
                     )}
                   </div>
@@ -353,7 +354,7 @@ export function BoardBackgroundModal({ open, onOpenChange }: BoardBackgroundModa
                     )}
                   >
                     {isProcessing ? (
-                      <Upload className="h-6 w-6 animate-spin text-muted-foreground" />
+                      <Spinner size="lg" />
                     ) : (
                       <ImageIcon className="h-6 w-6 text-muted-foreground" />
                     )}

apps/ui/src/components/dialogs/new-project-modal.tsx

@@ -14,16 +14,8 @@ import { Input } from '@/components/ui/input';
 import { Label } from '@/components/ui/label';
 import { Tabs, TabsContent, TabsList, TabsTrigger } from '@/components/ui/tabs';
 import { Badge } from '@/components/ui/badge';
-import {
-  FolderPlus,
-  FolderOpen,
-  Rocket,
-  ExternalLink,
-  Check,
-  Loader2,
-  Link,
-  Folder,
-} from 'lucide-react';
+import { FolderPlus, FolderOpen, Rocket, ExternalLink, Check, Link, Folder } from 'lucide-react';
+import { Spinner } from '@/components/ui/spinner';
 import { starterTemplates, type StarterTemplate } from '@/lib/templates';
 import { getElectronAPI } from '@/lib/electron';
 import { cn } from '@/lib/utils';
@@ -451,7 +443,7 @@ export function NewProjectModal({
           >
             {isCreating ? (
               <>
-                <Loader2 className="w-4 h-4 mr-2 animate-spin" />
+                <Spinner size="sm" className="mr-2" />
                 {activeTab === 'template' ? 'Cloning...' : 'Creating...'}
               </>
             ) : (

apps/ui/src/components/dialogs/workspace-picker-modal.tsx

@@ -8,7 +8,8 @@ import {
   DialogTitle,
 } from '@/components/ui/dialog';
 import { Button } from '@/components/ui/button';
-import { Folder, Loader2, FolderOpen, AlertCircle } from 'lucide-react';
+import { Folder, FolderOpen, AlertCircle } from 'lucide-react';
+import { Spinner } from '@/components/ui/spinner';
 import { getHttpApiClient } from '@/lib/http-api-client';
 
 interface WorkspaceDirectory {
@@ -74,7 +75,7 @@ export function WorkspacePickerModal({ open, onOpenChange, onSelect }: Workspace
         <div className="flex-1 overflow-y-auto py-4 min-h-[200px]">
           {isLoading && (
             <div className="flex flex-col items-center justify-center h-full gap-3">
-              <Loader2 className="w-8 h-8 text-brand-500 animate-spin" />
+              <Spinner size="xl" />
               <p className="text-sm text-muted-foreground">Loading projects...</p>
             </div>
           )}