feat: Implement TaskFlow logos and icons throughout the application

- Add favicon files (16x16 to 256x256, .ico)
- Add PWA icons (128, 256, 512, 1024)
- Add apple-touch-icon for iOS
- Add transparent icons for loading screens
- Add horizontal logo with tagline for auth page
- Update HTML head with proper favicon links
- Update PWA manifest with correct icon references
- Update sidebar header with branded icon
- Update mobile header with branded icon
- Update auth/login pages with logo display
- Update loading state with branded splash screen
- Update 404 page with logo header
- Update email template to use proper logo URL
- Update service worker and push notifications to use correct icons

client/src/pages/AuthPage.tsx

@@ -145,10 +145,13 @@ export default function AuthPage() {
 
     return (
         <div className="min-h-screen grid lg:grid-cols-2 dark">
-            <div className="hidden lg:flex flex-col justify-center items-center bg-zinc-900 p-12 text-white">
-                <div className="max-w-md space-y-4 text-center">
-                    <div className="mb-8">
-                        <img src="/favicon.png" alt="Logo" className="w-24 h-24" />
+            <div className="hidden lg:flex flex-col justify-center items-center bg-gradient-to-br from-zinc-900 via-zinc-900 to-violet-950 p-12 text-white">
+                <div className="max-w-md space-y-6 text-center">
+                    <div className="mb-8 flex flex-col items-center">
+                        <div className="w-28 h-28 rounded-2xl bg-gradient-to-br from-violet-600 to-indigo-600 flex items-center justify-center shadow-2xl mb-6">
+                            <img src="/icon-transparent-256.png" alt="TaskFlow" className="w-20 h-20 object-contain" />
+                        </div>
+                        <img src="/logo-horizontal-tagline-transparent.png" alt="TaskFlow - Focus. Flow. AI." className="h-12 object-contain" />
                     </div>
                     <h1 className="text-4xl font-bold tracking-tight">{t('auth.heroTitle')}</h1>
                     <p className="text-lg text-zinc-400">
@@ -162,7 +165,9 @@ export default function AuthPage() {
                     <Card className="w-full max-w-md shadow-xl border-border/50">
                         <CardHeader className="text-center space-y-2">
                             <div className="lg:hidden mx-auto mb-4">
-                                <img src="/favicon.png" alt="Logo" className="w-12 h-12 mx-auto" />
+                                <div className="w-14 h-14 rounded-xl bg-gradient-to-br from-violet-600 to-indigo-600 flex items-center justify-center shadow-lg mx-auto">
+                                    <img src="/icon-transparent-128.png" alt="TaskFlow" className="w-10 h-10 object-contain" />
+                                </div>
                             </div>
                             <CardTitle className="text-2xl font-bold">{t('auth.2faVerification')}</CardTitle>
                             <CardDescription>
@@ -194,7 +199,9 @@ export default function AuthPage() {
                     <Card className="w-full max-w-md shadow-xl border-border/50">
                         <CardHeader className="text-center space-y-2">
                             <div className="lg:hidden mx-auto mb-4">
-                                <img src="/favicon.png" alt="Logo" className="w-12 h-12 mx-auto" />
+                                <div className="w-14 h-14 rounded-xl bg-gradient-to-br from-violet-600 to-indigo-600 flex items-center justify-center shadow-lg mx-auto">
+                                    <img src="/icon-transparent-128.png" alt="TaskFlow" className="w-10 h-10 object-contain" />
+                                </div>
                             </div>
                             <CardTitle className="text-2xl font-bold">{t('auth.welcomeBack')}</CardTitle>
                             <CardDescription>