feat: add long-press context menus for mobile messages

Create useLongPress hook with 500ms delay, 10px movement cancellation
(Euclidean distance), and ghost click suppression. Integrate into
Message component to trigger the existing context menu bottom sheet
on touch devices.

packages/web/src/components/chat/Message.tsx

@@ -16,6 +16,7 @@ import { Username } from '../ui/Username';
 import { EmojiPicker } from './EmojiPicker';
 import { hasPermissionBit, PermissionBits } from '../../utils/permissions';
 import { isSelf, resolveDisplayIdentity } from '../../utils/identity';
+import { useLongPress } from '../../hooks/useLongPress';
 
 interface MessageProps {
   message: MessageWithUser;
@@ -201,6 +202,36 @@ export function Message({ message, isCompact, isFirstInGroup, previousMessageId
     useContextMenuStore.getState().open({ x: e.clientX, y: e.clientY }, items);
   };
 
+  const isMobile = useUIStore((s) => s.isMobile);
+
+  const longPressHandlers = useLongPress((position) => {
+    const selectedText = window.getSelection()?.toString() ?? '';
+    const items = buildMessageMenuItems({
+      message,
+      selectedText,
+      previousMessageId,
+      isAuthor,
+      isDm: isDmMessage,
+      canAddReactions,
+      canSendMessages,
+      canManageMessages,
+      onReply: () => setReplyTo(message),
+      onEdit: () => {
+        setEditContent(message.content ?? '');
+        setIsEditing(true);
+      },
+      onDelete: () => deleteMessage(message.id, channelKey),
+      onReaction: (emoji: string) => toggleReaction(emoji),
+      onOpenEmojiPicker: () => {
+        useContextMenuStore.getState().close();
+        setShowReactionPicker(true);
+      },
+      onMarkUnread: (msgId: string) => markUnread(channelKey, msgId),
+    });
+    if (items.length === 0) return;
+    useContextMenuStore.getState().open({ x: position.clientX, y: position.clientY }, items);
+  });
+
   const handleEditSubmit = async (e: React.KeyboardEvent) => {
     if (e.key === 'Enter' && !e.shiftKey) {
       e.preventDefault();
@@ -524,7 +555,7 @@ export function Message({ message, isCompact, isFirstInGroup, previousMessageId
   );
 
   return (
-    <div onContextMenu={handleContextMenu}>
+    <div onContextMenu={handleContextMenu} {...(isMobile ? longPressHandlers : {})}>
       {content}
     </div>
   );