iOS: existing DM opens with a blank message pane while Desktop shows the conversation

**Describe the bug**
On Buzz mobile for iPhone, opening an existing direct-message conversation can show the conversation header and composer but a completely blank message area. The same DM renders its full message history correctly in Buzz Desktop at the same time, so the events exist and are available to another client.

This appears to be a mobile retrieval/rendering problem rather than failed message delivery.

**Steps to reproduce**
1. Exchange messages in a DM containing human and agent messages.
2. Confirm the conversation and message history are visible in Buzz Desktop.
3. Open the same DM in Buzz on iPhone.
4. Observe that the conversation opens, but the message pane is blank.

**Expected behavior**
The iPhone app should render the same DM history that is visible on Desktop.

**Actual behavior**
The DM shell opens on iPhone, but no chat messages are displayed. Desktop continues to display the conversation correctly.

**Version and platform**
- Buzz mobile version: 0.4.12
- Mobile OS: iOS/iPhone (exact OS version unknown)
- Buzz Desktop version: 0.5.3 (0.5.3)
- Desktop OS: macOS
- Relay: managed `communities.buzz.xyz` relay

**Logs / additional context**
- Reproduced on 2026-08-02.
- The relay-backed Desktop client displayed the messages while the mobile client was blank.
- This resembles the missing-DM-message symptom in #2971, but that report is Android-specific and combines it with a presence bug. This report confirms the blank DM behavior on iOS.
- Screenshots were captured showing the same conversation on Desktop and the blank mobile view. They contain private DM content and can be provided privately to maintainers if needed.