feat: phone login, position badge, logout in profile, global search, admin chats

- Login: by phone number instead of username
- Position field: shown as badge next to name in members list, search, admin panel
- Logout: moved from sidebar to profile modal settings
- Sidebar search: global — shows matching users with one-click private chat
- Admin panel: new Чаты tab showing all chats with delete, position/phone in user form
- Backend: /api/admin/chats endpoint, position column migration, phone login support

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/routes/chats.ts

@@ -80,7 +80,7 @@ export default async function chatRoutes(app: FastifyInstance) {
     if (!chat) return reply.status(404).send({ error: 'Not found' });
 
     const { rows: members } = await pool.query(`
-      SELECT u.id, u.username, u.display_name, u.avatar_color, u.avatar, u.last_seen, cm.role, cm.can_send_messages
+      SELECT u.id, u.username, u.display_name, u.avatar_color, u.avatar, u.position, u.last_seen, cm.role, cm.can_send_messages
       FROM chat_members cm
       JOIN users u ON u.id = cm.user_id
       WHERE cm.chat_id = $1
@@ -104,6 +104,7 @@ export default async function chatRoutes(app: FastifyInstance) {
       members: members.map(m => ({
         id: m.id, username: m.username, displayName: m.display_name,
         avatarColor: m.avatar_color, avatar: m.avatar || null,
+        position: m.position || null,
         role: m.role, online: onlineSet.has(m.id),
         lastSeen: m.last_seen, canSendMessages: m.can_send_messages,
       })),