feat: Implement username/password authentication and registration features

app/lib/avatar.ts

@@ -0,0 +1,48 @@
+const COLORS = [
+  '#2196F3', // 蓝色
+  '#009688', // 青色
+  '#9C27B0', // 紫色
+  '#F44336', // 红色
+  '#673AB7', // 深紫色
+  '#3F51B5', // 靛蓝
+  '#4CAF50', // 绿色
+  '#FF5722', // 深橙
+  '#795548', // 棕色
+  '#607D8B', // 蓝灰
+];
+
+export function generateAvatarUrl(name: string): string {
+  const initial = name[0].toUpperCase();
+  
+  const colorIndex = Array.from(name).reduce(
+    (acc, char) => acc + char.charCodeAt(0), 0
+  ) % COLORS.length;
+  
+  const backgroundColor = COLORS[colorIndex];
+  
+  const svg = `
+    <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+      <rect width="100" height="100" fill="${backgroundColor}"/>
+      <text 
+        x="50%" 
+        y="50%" 
+        fill="white" 
+        font-family="system-ui, -apple-system, sans-serif" 
+        font-size="45" 
+        font-weight="500"
+        text-anchor="middle"
+        alignment-baseline="central"
+        dominant-baseline="central"
+        style="text-transform: uppercase"
+      >
+        ${initial}
+      </text>
+    </svg>
+  `.trim();
+
+  const encoder = new TextEncoder();
+  const bytes = encoder.encode(svg);
+  const base64 = Buffer.from(bytes).toString('base64');
+  
+  return `data:image/svg+xml;base64,${base64}`;
+}