Address PR review comments:
- Remove pathUtils.ts and move sanitize/encodePath directly into utils.ts
- Simplify dual-key approach to single key using encodePath for map keys
- Remove backward-compat logic (not needed per reviewer)
- Update tests to match simplified approach
Use encodePath only for internal map key grouping (collision-free) and
sanitize for Traefik-facing router/service names (unchanged for existing
users). Extract pure functions into pathUtils.ts so tests can run without
DB dependencies.