fix(chat): make home chat scroll on linux

WebKitGTK (Tauri's Linux webview) strictly enforces flex items' default
min-height: auto, so flex-1 + overflow-y-auto never scrolled — the message
list grew with content and pushed the composer off-screen.

Adding min-h-0 lets the flex item shrink below content height so
overflow-y-auto actually engages. No-op on Chromium/macOS where this was
already permissive.

Resolves: [2026-05-24] — Fix home chat scroll on Linux (Tauri/WebKitGTK)

Author: kaizen403

apps/desktop-ui/components/chat/chat-message-list.tsx

@@ -43,7 +43,7 @@ export function ChatMessageList({
   if (messages.length === 0 && !showThinking) return null;
 
   return (
-    <div className={cn("flex-1 overflow-y-auto px-4 py-6", className)}>
+    <div className={cn("min-h-0 flex-1 overflow-y-auto px-4 py-6", className)}>
       <div className="mx-auto max-w-3xl space-y-4">
         {messages.map((msg, i) => (
           <ChatMessage key={i} message={msg} />