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/public/manifest.json

@@ -1,7 +1,7 @@
 {
   "name": "TaskFlow",
   "short_name": "TaskFlow",
-  "description": "Gamified task management with AI assistance",
+  "description": "Gamified task management with AI assistance. Focus. Flow. AI.",
   "start_url": "/",
   "display": "standalone",
   "background_color": "#0f0f23",
@@ -9,16 +9,31 @@
   "orientation": "portrait-primary",
   "icons": [
     {
-      "src": "/favicon.png",
-      "sizes": "192x192",
-      "type": "image/png",
-      "purpose": "any maskable"
+      "src": "/icon-128.png",
+      "sizes": "128x128",
+      "type": "image/png"
     },
     {
-      "src": "/favicon.png",
+      "src": "/icon-256.png",
+      "sizes": "256x256",
+      "type": "image/png"
+    },
+    {
+      "src": "/icon-512.png",
       "sizes": "512x512",
       "type": "image/png",
-      "purpose": "any maskable"
+      "purpose": "any"
+    },
+    {
+      "src": "/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "maskable"
+    },
+    {
+      "src": "/icon-1024.png",
+      "sizes": "1024x1024",
+      "type": "image/png"
     }
   ],
   "categories": ["productivity", "utilities"],