[Bug]: Backend startup crashes leave desktop blank with no visible error

Before submitting

• I searched existing issues and did not find a duplicate of this specific failure.
• I included enough detail to reproduce or investigate the problem.

Area

apps/desktop

Steps to reproduce

1. Launch desktop with a backend that fails during startup (observed: a missing SQLite column).
2. The backend exits repeatedly before it can serve the renderer.

Expected behavior

Show a backend-independent startup error with the failure reason and a way to retry or open/copy logs.

Actual behavior

Completely black window. Electron DevTools has no useful error; Network shows a failed t3code://app request. Restarting/reinstalling does not explain the failure.

Production serves the initial UI through the backend. DesktopWindow.ts swallows loadURL() rejection and only logs did-fail-load; backend restart handling keeps retrying without a visible terminal failure state. Frontend error handling cannot run because the page never loads.

Related: #9239 reports a Linux credential-store startup stall; this is a confirmed backend process crash on macOS.

Impact

Blocks work completely

Version or commit

0.0.39 and 0.0.40-nightly.20260907.1346

Environment

macOS 26.6.2 (also occurred before the macOS update), Electron desktop.

Logs or stack traces

Error: no such column: branch_pull_request_json
backend child exits with code=1
ECONNREFUSED 127.0.0.1:3773

The database error is a separate cause; this issue concerns the absence of visible diagnostics when startup fails.

Start in apps/desktop/DesktopWindow.ts, especially the loadURL rejection and did-fail-load handling, then trace the backend restart path that keeps retrying after a crash. Reproduce the failure with a backend that exits during startup and verify that the desktop shows the failure reason, offers retry, and provides a way to open or copy logs.