feat: notes to self via self-DM

Backend:
- Removed self-DM restriction in conversation Create
- Added duplicate check for self-DMs (returns existing one)

Frontend:
- ConversationList: [📝] button creates/opens notes to self
- Self-DMs show as 'Notes' with 📝 icon in sidebar
- DMChat header shows 'Notes' for self-DMs

web/src/components/ConversationList.tsx

@@ -8,11 +8,16 @@ function otherMemberName(conv: { members: { id: string; username: string }[] },
   return other?.username || "unknown";
 }
 
+function isSelfDM(conv: { members: { id: string }[] }, currentUserId: string) {
+  return conv.members.length === 1 && conv.members[0].id === currentUserId;
+}
+
 export function ConversationList() {
   const conversations = useConversationStore((s) => s.conversations);
   const activeId = useConversationStore((s) => s.activeConversationId);
   const fetchConversations = useConversationStore((s) => s.fetchConversations);
   const setActive = useConversationStore((s) => s.setActiveConversation);
+  const createConversation = useConversationStore((s) => s.createConversation);
   const currentUser = useAuthStore((s) => s.user);
   const [showNew, setShowNew] = useState(false);
 
@@ -20,25 +25,48 @@ export function ConversationList() {
     fetchConversations();
   }, [fetchConversations]);
 
+  const openNotes = async () => {
+    // Find existing self-DM or create one
+    const existing = conversations.find((c) => isSelfDM(c, currentUser?.id || ""));
+    if (existing) {
+      setActive(existing.id);
+      return;
+    }
+    try {
+      await createConversation([]);
+    } catch { /* ignore */ }
+  };
+
   return (
     <div className="h-full w-56 bg-gb-bg-s border-r border-gb-bg-t flex flex-col">
       <div className="terminal-border border-t-0 border-x-0 px-3 py-2 text-gb-fg truncate flex items-center justify-between">
         <span>[DIRECT MESSAGES]</span>
-        <button
-          onClick={() => setShowNew(true)}
-          className="terminal-button text-xs"
-          title="New conversation"
-        >
-          [+]
-        </button>
+        <div className="flex gap-1">
+          <button
+            onClick={openNotes}
+            className="terminal-button text-xs"
+            title="Notes to self"
+          >
+            [📝]
+          </button>
+          <button
+            onClick={() => setShowNew(true)}
+            className="terminal-button text-xs"
+            title="New conversation"
+          >
+            [+]
+          </button>
+        </div>
       </div>
       <div className="flex-1 overflow-y-auto p-2 font-mono text-sm">
         {conversations.length === 0 && (
           <p className="text-gb-fg-f">[no conversations]</p>
         )}
         {conversations.map((conv) => {
-          const name =
-            conv.type === "group_dm"
+          const self = isSelfDM(conv, currentUser?.id || "");
+          const name = self
+            ? "Notes"
+            : conv.type === "group_dm"
               ? conv.name || conv.members.map((m) => m.username).join(", ")
               : otherMemberName(conv, currentUser?.id || "");
           return (
@@ -51,7 +79,7 @@ export function ConversationList() {
                   : "hover:bg-gb-bg-t text-gb-fg-s"
               }`}
             >
-              <span className="text-gb-fg-f">@</span>
+              <span className="text-gb-fg-f">{self ? "📝" : "@"}</span>
               <span className="truncate">{name}</span>
             </button>
           );