Task #45: Tapping a chat notification opens the matching conversation

- notifications.tsx: When a notification is clicked, if it has
  relatedType === "conversation" and a relatedId, navigate to
  /chat?c=<conversationId> in addition to marking it read. Other
  notification types continue to behave as before (just mark read).
- chat.tsx: Read the optional `c` query parameter via wouter's
  useSearch hook. When present and valid, set it as the
  selectedConvId so the conversation opens automatically, then
  replace the URL back to /chat so refreshing or navigating away
  doesn't keep re-opening it.

No API or schema changes required; notification records already
carry relatedType/relatedId for chat notifications.

artifacts/teaboy-os/src/pages/chat.tsx

@@ -1,6 +1,6 @@
 import { useState, useEffect, useRef, useMemo } from "react";
 import { useTranslation } from "react-i18next";
-import { useLocation } from "wouter";
+import { useLocation, useSearch } from "wouter";
 import {
   useListConversations,
   getListConversationsQueryKey,
@@ -135,6 +135,7 @@ type ConvMode = "direct" | "group";
 export default function ChatPage() {
   const { t, i18n } = useTranslation();
   const [, setLocation] = useLocation();
+  const search = useSearch();
   const { user } = useAuth();
   const lang = i18n.language;
   const isRtl = lang === "ar";
@@ -231,6 +232,17 @@ export default function ChatPage() {
     };
   }, [user, selectedConvId, queryClient]);
 
+  // Open conversation specified via ?c=<id> query param (e.g. from notifications)
+  useEffect(() => {
+    const params = new URLSearchParams(search);
+    const convParam = params.get("c");
+    if (!convParam) return;
+    const convId = Number(convParam);
+    if (!Number.isFinite(convId) || convId <= 0) return;
+    setSelectedConvId(convId);
+    setLocation("/chat", { replace: true });
+  }, [search, setLocation]);
+
   // Mark conversation as read when selected
   useEffect(() => {
     if (selectedConvId) {

artifacts/teaboy-os/src/pages/notifications.tsx

@@ -49,6 +49,20 @@ export default function NotificationsPage() {
     );
   };
 
+  const handleNotificationClick = (n: {
+    id: number;
+    isRead: boolean;
+    relatedType?: string | null;
+    relatedId?: number | null;
+  }) => {
+    if (!n.isRead) {
+      handleMarkOne(n.id);
+    }
+    if (n.relatedType === "conversation" && n.relatedId != null) {
+      setLocation(`/chat?c=${n.relatedId}`);
+    }
+  };
+
   const unreadCount = notifications?.filter((n) => !n.isRead).length ?? 0;
 
   return (
@@ -103,7 +117,7 @@ export default function NotificationsPage() {
             return (
               <div
                 key={n.id}
-                onClick={() => !n.isRead && handleMarkOne(n.id)}
+                onClick={() => handleNotificationClick(n)}
                 className={`glass-panel rounded-2xl p-4 cursor-pointer transition-opacity ${n.isRead ? "opacity-60" : ""}`}
               >
                 <div className="flex items-start justify-between gap-2">