feat(profile): enhance avatar handling and improve layout for profile header

components/public/profile-header.tsx

@@ -1,4 +1,7 @@
 /* eslint-disable @next/next/no-img-element */
+"use client";
+
+import { useMemo, useState } from "react";
 type ProfileHeaderProps = {
   displayName: string;
   username: string;
@@ -7,34 +10,67 @@ type ProfileHeaderProps = {
 };
 
 export function ProfileHeader({ displayName, username, bio, avatarUrl }: ProfileHeaderProps) {
-  const words = displayName.trim().split(/\s+/).filter(Boolean);
-  const initials =
-    words.length >= 2
-      ? `${words[0]?.[0] ?? ""}${words[1]?.[0] ?? ""}`.toUpperCase()
-      : (words[0]?.slice(0, 2) ?? username.slice(0, 2)).toUpperCase();
+  const [avatarFailed, setAvatarFailed] = useState(false);
+
+  const initials = useMemo(() => {
+    const words = displayName.trim().split(/\s+/).filter(Boolean);
+    if (words.length >= 2) {
+      return `${words[0]?.[0] ?? ""}${words[1]?.[0] ?? ""}`.toUpperCase();
+    }
+    if (words.length === 1) {
+      return (words[0]?.[0] ?? username[0] ?? "?").toUpperCase();
+    }
+    return (username[0] ?? "?").toUpperCase();
+  }, [displayName, username]);
+
+  const normalizedAvatarUrl = avatarUrl?.trim() ?? "";
+  const hasValidAvatarUrl = useMemo(() => {
+    if (!normalizedAvatarUrl) {
+      return false;
+    }
+    try {
+      const url = new URL(normalizedAvatarUrl);
+      if (url.protocol !== "http:" && url.protocol !== "https:") {
+        return false;
+      }
+      // Reject placeholder-like values such as "https://..."
+      if (!url.hostname || url.hostname === "..." || !url.hostname.includes(".")) {
+        return false;
+      }
+      return true;
+    } catch {
+      return false;
+    }
+  }, [normalizedAvatarUrl]);
+
+  const shouldShowAvatar = hasValidAvatarUrl && !avatarFailed;
 
   return (
     <header className="terminal-card space-y-4">
-      <div className="flex items-center gap-4">
-        {avatarUrl ? (
+      <div className="flex items-start">
+        {shouldShowAvatar ? (
           <img
-            src={avatarUrl}
+            src={normalizedAvatarUrl}
             alt={`${displayName} avatar`}
-            className="h-16 w-16 rounded-full border border-border object-cover"
+            className="shrink-0 rounded-sm border border-border object-cover"
+            style={{ width: 160, height: 160 }}
+            onError={() => setAvatarFailed(true)}
           />
         ) : (
-          <div className="flex h-16 w-16 items-center justify-center rounded-full border border-border bg-panel text-lg font-semibold text-muted">
+          <div
+            className="flex shrink-0 items-center justify-center rounded-sm border border-border bg-panel text-[5.5rem] font-semibold leading-none text-muted md:text-[6.5rem]"
+            style={{ width: 160, height: 160 }}
+          >
             {initials}
           </div>
         )}
 
-        <div className="space-y-1.5">
-          <h1 className="text-3xl font-bold leading-tight">{displayName}</h1>
-          <p className="text-sm text-muted">@{username}</p>
+        <div className="min-h-[160px] space-y-2 pt-1" style={{ marginLeft: 40 }}>
+          <h1 className="text-5xl font-bold leading-tight tracking-[0.01em]">{displayName}</h1>
+          <p className="text-xl text-muted">@{username}</p>
+          {bio ? <p className="max-w-2xl pt-2 text-sm leading-relaxed text-muted">{bio}</p> : null}
         </div>
       </div>
-
-      {bio ? <p className="max-w-2xl text-sm leading-relaxed text-muted">{bio}</p> : null}
     </header>
   );
 }