Send system messages for group rename / add / remove

Original task (#38): When admins rename a group or add/remove members,
post a system message into the chat thread so other members see who
changed what and when, with bilingual (AR/EN) text and real-time
delivery.

Changes
- lib/db/src/schema/conversations.ts: added `kind` (varchar default
  "user") and `meta` (jsonb) columns on the `messages` table. Pushed
  the new columns directly via ALTER TABLE since drizzle-kit push
  prompted on unrelated rename ambiguities. Also healed pre-existing
  schema drift on `users.clock_hour12`,
  `conversations.avatar_url`, and
  `conversation_participants.is_muted/is_archived` so the API could
  start.
- lib/api-spec/openapi.yaml: extended MessageWithSender with `kind`
  (enum: user | group_renamed | members_added | member_removed) and
  optional `meta`. Re-ran codegen.
- artifacts/api-server/src/routes/conversations.ts: added
  insertAndEmitSystemMessage + small user-display helpers; PATCH
  conversation now emits a `group_renamed` system message when a
  name actually changes; add-participants emits `members_added` with
  the actor + added users; remove-participant emits `member_removed`
  with actor + removed user. Each system message is broadcast over
  Socket.IO via the existing `new_message` channel so all current
  members receive it immediately.
- artifacts/teaboy-os/src/pages/chat.tsx: render messages with
  `kind != "user"` as centered, muted pill bubbles (no avatar /
  sender label) using a new renderSystemMessage helper that picks
  the language-appropriate name out of meta. Conversation list
  preview also uses it so the last activity reads sensibly when the
  most recent message is a system message.
- artifacts/teaboy-os/src/locales/{en,ar}.json: added chat.system.*
  strings (groupRenamed, membersAdded with plural variants,
  memberRemoved, someone, listSeparator).

Verification
- Typecheck (libs + artifacts) passes.
- e2e via testing skill: registered fresh users, created a group,
  renamed it, added a member, removed a member; all three centered
  system messages appeared in the thread in order with the expected
  copy.

Notes / deviations
- Used the actor's userId as senderId for system messages (kept
  existing NOT NULL FK) instead of introducing a nullable sender,
  which keeps the migration lightweight. This means system messages
  count toward unread for non-actor members; flagged as a follow-up.

Replit-Task-Id: 6dfa2b99-fbac-4146-b59b-8c04a14c9e96

artifacts/api-server/src/routes/conversations.ts

@@ -284,6 +284,10 @@ router.patch("/conversations/:id", requireAuth, async (req, res): Promise<void>
     return;
   }
 
+  const nameChanged =
+    (updates.nameAr !== undefined && updates.nameAr !== conv.nameAr) ||
+    (updates.nameEn !== undefined && updates.nameEn !== conv.nameEn);
+
   if (Object.keys(updates).length > 0) {
     await db
       .update(conversationsTable)
@@ -291,6 +295,17 @@ router.patch("/conversations/:id", requireAuth, async (req, res): Promise<void>
       .where(eq(conversationsTable.id, params.data.id));
   }
 
+  if (nameChanged) {
+    const actor = await getUserDisplay(userId);
+    await insertAndEmitSystemMessage(params.data.id, userId, "group_renamed", {
+      actor,
+      oldNameAr: conv.nameAr,
+      oldNameEn: conv.nameEn,
+      newNameAr: finalNameAr,
+      newNameEn: finalNameEn,
+    });
+  }
+
   const details = await buildConversationDetails(params.data.id, userId);
   if (!details) {
     res.status(404).json({ error: "Conversation not found" });
@@ -313,6 +328,80 @@ async function evictUserFromConversationRoom(
   }
 }
 
+type SystemMessageMeta = Record<string, unknown>;
+
+async function getUserDisplay(userId: number): Promise<{
+  id: number;
+  username: string;
+  displayNameAr: string | null;
+  displayNameEn: string | null;
+} | null> {
+  const [u] = await db
+    .select({
+      id: usersTable.id,
+      username: usersTable.username,
+      displayNameAr: usersTable.displayNameAr,
+      displayNameEn: usersTable.displayNameEn,
+    })
+    .from(usersTable)
+    .where(eq(usersTable.id, userId));
+  return u ?? null;
+}
+
+async function getUsersDisplay(userIds: number[]): Promise<
+  Array<{
+    id: number;
+    username: string;
+    displayNameAr: string | null;
+    displayNameEn: string | null;
+  }>
+> {
+  if (userIds.length === 0) return [];
+  return db
+    .select({
+      id: usersTable.id,
+      username: usersTable.username,
+      displayNameAr: usersTable.displayNameAr,
+      displayNameEn: usersTable.displayNameEn,
+    })
+    .from(usersTable)
+    .where(sql`${usersTable.id} IN (${sql.join(userIds.map((id) => sql`${id}`), sql`, `)})`);
+}
+
+async function insertAndEmitSystemMessage(
+  conversationId: number,
+  actorId: number,
+  kind: string,
+  meta: SystemMessageMeta,
+): Promise<void> {
+  const [msg] = await db
+    .insert(messagesTable)
+    .values({
+      conversationId,
+      senderId: actorId,
+      content: "",
+      kind,
+      meta,
+    })
+    .returning();
+
+  const [sender] = await db
+    .select({
+      id: usersTable.id,
+      username: usersTable.username,
+      displayNameAr: usersTable.displayNameAr,
+      displayNameEn: usersTable.displayNameEn,
+      avatarUrl: usersTable.avatarUrl,
+      isAdmin: sql<boolean>`false`,
+    })
+    .from(usersTable)
+    .where(eq(usersTable.id, actorId));
+
+  const fullMessage = { ...msg, sender };
+  const { io } = await import("../index.js");
+  io.to(`conversation:${conversationId}`).emit("new_message", fullMessage);
+}
+
 async function emitConversationUpdate(conversationId: number): Promise<void> {
   const { io } = await import("../index.js");
   const members = await db
@@ -410,6 +499,15 @@ router.post(
           })),
         )
         .onConflictDoNothing();
+
+      const [actor, addedUsers] = await Promise.all([
+        getUserDisplay(userId),
+        getUsersDisplay(validIds),
+      ]);
+      await insertAndEmitSystemMessage(params.data.id, userId, "members_added", {
+        actor,
+        addedUsers,
+      });
     }
 
     const details = await buildConversationDetails(params.data.id, userId);
@@ -443,17 +541,29 @@ router.delete(
       return;
     }
 
-    await db
+    const deleted = await db
       .delete(conversationParticipantsTable)
       .where(
         and(
           eq(conversationParticipantsTable.conversationId, params.data.id),
           eq(conversationParticipantsTable.userId, params.data.userId),
         ),
-      );
+      )
+      .returning({ userId: conversationParticipantsTable.userId });
 
     await evictUserFromConversationRoom(params.data.userId, params.data.id);
 
+    if (deleted.length > 0) {
+      const [actor, removedUser] = await Promise.all([
+        getUserDisplay(userId),
+        getUserDisplay(params.data.userId),
+      ]);
+      await insertAndEmitSystemMessage(params.data.id, userId, "member_removed", {
+        actor,
+        removedUser,
+      });
+    }
+
     const details = await buildConversationDetails(params.data.id, userId);
     if (!details) {
       res.status(404).json({ error: "Conversation not found" });