feat(arayüz): logo ve uygulama ikonları

- Logo: indigo zemin, spiral defter ve ¥ (frontend/brand/*.svg)
- scripts/icons.sh (npm run icons): favicon (svg/ico), PWA 192/512, maskable, Apple touch icon, Tauri 1024
- Logo bileşeni (components/logo.tsx)
- index.html: ikon bağlantıları, theme-color, açıklama

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/public/favicon.svg

@@ -0,0 +1,23 @@
+<!-- Kakeibo logosu (ana kaynak). Değiştirirseniz: scripts/icons.sh -->
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
+  <defs>
+    <linearGradient id="kakeibo-bg" x1="0" y1="0" x2="0" y2="1">
+      <stop offset="0" stop-color="#3b4aa8"/>
+      <stop offset="1" stop-color="#26307a"/>
+    </linearGradient>
+  </defs>
+  <rect width="512" height="512" rx="112" fill="url(#kakeibo-bg)"/>
+  <g id="mark">
+    <rect x="140" y="92" width="252" height="328" rx="28" fill="#f7f3ea"/>
+    <rect x="140" y="92" width="52" height="328" rx="28" fill="#e6dfcf"/>
+    <rect x="166" y="92" width="26" height="328" fill="#e6dfcf"/>
+    <g fill="#26307a">
+      <circle cx="140" cy="150" r="13"/><circle cx="140" cy="220" r="13"/>
+      <circle cx="140" cy="290" r="13"/><circle cx="140" cy="360" r="13"/>
+    </g>
+    <g fill="none" stroke="#26307a" stroke-width="22" stroke-linecap="round" stroke-linejoin="round">
+      <path d="M238 178 L292 254 L346 178"/><path d="M292 254 V342"/>
+      <path d="M250 266 H334"/><path d="M250 304 H334"/>
+    </g>
+  </g>
+</svg>