fix(gui): recent repos keep and reopen --git-dir/--work-tree repos (#5942)

[yzxcj797]

Closes #5942.

The two failures, per the issue

1. The entry disappears from the menu. newRecentReposList kept an entry only if <path>/.git exists. A dotfile repo's work tree has no .git, so the next run in any other repo dropped it from the list.
2. Even while the entry survives, switching fails. The menu's OnPress called switchTo(path), which clears GIT_DIR/GIT_WORK_TREE and chdirs; VerifyInGitRepo then fails because nothing at the work tree's path leads to the git dir.

The root cause is exactly the gap the 2020 comment in updateRecentRepoList described: AppState.RecentRepos is []string — nowhere to remember how the repo was found. #5910's RepoLocation.GitLocationEnvVars provides the mechanism; this wires the recent-repos list to it.

The fix

• AppState gains RecentRepoLocations []RecentRepoLocation (pkg/config/recent_repo_location.go): one entry per recently-opened repo carrying the environment needed to reopen it — empty for every repo git finds from the work tree.
• The legacy plain-path list is still written in parallel with the env-less repos, so an older lazygit reading the same state file keeps working (rollback-safe); a state file last written by an older version is folded into the richer list on first write.
• updateRecentRepoList no longer skips dotfile repos — bare repos are still skipped (no work tree to change back to) — and records the process's GIT_DIR/GIT_WORK_TREE on the entry. Directory-less entries still age out.
• The menu's OnPress routes through switchToLocation, which restores that environment before chdir and re-verifies through git — the exact path the repo-path stack already takes.

Out of scope (noted for follow-up)

The startup path (pkg/app/app.go openRecentRepo) still walks the legacy list — the shared verify/direnv flow there runs before the gui exists, so wiring it deserves its own change with its own testing. With this PR, the entry at least survives in state and the menu can return to the repo within a session.

Tests

Three in pkg/gui/recent_repos_panel_test.go: a dotfile entry survives list rebuilds with its env intact (and a vanished directory still ages out), a legacy env-less entry without .git still ages out (preserving the old contract), and the legacy-list migration prepends the current repo with empty env. (No Go toolchain on this Windows machine — the compile gate is CI; the diff uses only os/path/filepath/testing and existing package types.)