fix(jobs): mirror sync killed by 1-minute default timeout, leaving repos in broken state

[dvrd]

Summary

Mirror sync commands (git fetch --prune and git remote update --prune) in pkg/jobs/mirror.go inherit the 1-minute DefaultTimeout from the git-module library because no explicit timeout is set. For repos whose network fetch takes longer than 1 minute, the git process is killed mid-transfer: --prune has already removed local refs that no longer exist on remote, but new/renamed remote refs were never fully fetched before the timeout. The result is missing or stale branches.

Root cause

// pkg/jobs/mirror.go
cmd := git.NewCommand(args...).WithContext(ctx)
// No .WithTimeout(-1) → falls through to DefaultTimeout = 1 minute

The initial import in ImportRepository correctly sets Timeout: -1 (no timeout) to allow arbitrarily large clones. The sync job never applies this same protection.

Fix

Add .WithTimeout(-1) to both sync commands, mirroring the clone behavior.

Closes #633