fix(server): stop background status fetches after repeated timeouts

[macodev00]

What Changed

Background upstream refresh stops polling a remote after three consecutive git fetch timeouts and reports that upstream status needs attention. Silent credential-helper success is unchanged. An explicit pull, push, or fetch still runs, and a success resumes background refresh.

Why

GitVcsDriver.fetchRemoteForStatus fetches with a 5s timeout. On macOS, Homebrew git uses credential.helper=osxkeychain. After a git upgrade the helper can raise a Security-framework password dialog that those 5s kills before Always Allow can be stored. Failures were backed off forever (30s up to 15 minutes), so the prompt kept returning, especially on window focus.

Clearing credential.helper on every background fetch would also drop silent keychain and gh auth git-credential success. The background env is unchanged. Explicit git pull --ff-only still has no non-interactive env and a 30s timeout, so the dialog can be approved.

UI Changes

Git actions on web and desktop show “Upstream status needs attention. Pull to refresh it.” The mobile git header and overview say the upstream needs attention, and the overview offers Pull when the branch is not already behind.

Screenshots were not captured here; the browser panel is not available in this environment.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Fixes pingdotgg#13912