Squash-merges PR #614. Fixes Docker 500-on-every-request crash from PermissionError in load_settings() (issue #570 follow-up).
Both SETTINGS_FILE.exists() call sites now catch OSError and fall back to defaults. Reviewer nits addressed: removed unused imports/var in tests, improved log message to say "inaccessible?" instead of "permission denied?". Rebased clean onto v0.50.73. 1373 tests passing, QA harness green.
