feat(frontend): Update brand identity with new logo and color scheme.

- Add new Logo component with gradient design (blue #0b74de to cyan #06b6d4)
- Replace CreditCard icon with custom Logo in sidebar
- Update primary and secondary theme colors to match brand gradient
- Regenerate all PWA icons with new logo design
- Update theme colors in PWA manifest and meta tags
- Fix ESLint config to ignore generated PWA files

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/index.html

@@ -6,7 +6,7 @@
     <link rel="icon" href="/favicon.svg" sizes="any" type="image/svg+xml" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover" />
     <title>Leggen</title>
-    
+
     <!-- PWA Meta Tags -->
     <meta name="description" content="Personal finance management application" />
     <meta name="application-name" content="Leggen" />
@@ -16,19 +16,19 @@
     <meta name="format-detection" content="telephone=no" />
     <meta name="mobile-web-app-capable" content="yes" />
     <meta name="msapplication-config" content="/browserconfig.xml" />
-    <meta name="msapplication-TileColor" content="#3B82F6" />
+    <meta name="msapplication-TileColor" content="#0b74de" />
     <meta name="msapplication-tap-highlight" content="no" />
-    
+
     <!-- Dynamic theme-color - will be updated by JavaScript -->
-    <meta name="theme-color" content="#ffffff" id="theme-color-meta" />
-    <meta name="msapplication-navbutton-color" content="#ffffff" id="ms-theme-color-meta" />
+    <meta name="theme-color" content="#0b74de" id="theme-color-meta" />
+    <meta name="msapplication-navbutton-color" content="#0b74de" id="ms-theme-color-meta" />
     <meta name="apple-mobile-web-app-status-bar-style" content="default" id="apple-status-bar-meta" />
-    
+
     <!-- Icons -->
     <link rel="apple-touch-icon" href="/apple-touch-icon-180x180.png" />
-    <link rel="mask-icon" href="/favicon.svg" color="#3B82F6" />
+    <link rel="mask-icon" href="/favicon.svg" color="#0b74de" />
     <link rel="shortcut icon" href="/favicon.ico" />
-    
+
     <!-- Manifest -->
     <link rel="manifest" href="/manifest.webmanifest" />
   </head>