[Low] R2 errors swallowed without logging — outages invisible in server logs

[bmersereau]

Problem

backend/src/lib/storage.ts — both downloadFile and getSignedUrl silently swallow all errors:

export async function downloadFile(key: string): Promise<ArrayBuffer | null> {
  ...
  try { ... }
  catch { return null; }  // no logging
}

export async function getSignedUrl(...): Promise<string | null> {
  ...
  try { ... }
  catch { return null; }  // no logging
}

When R2 is misconfigured or unreachable, callers receive null and return 404/503 to the client. There is no server-side log entry, making R2 outages completely invisible until users report them.

Fix

Add console.error("[storage] downloadFile failed", { key, error: err }) (and equivalent for getSignedUrl) in the catch blocks before returning null.