Knulli native integration: cached-ids export, batch cache CLI, service-aware menu

[misantronic]

Linux-side changes for the Knulli native integration (companion to knulli-cfw/knulli-linux#94 and knulli-cfw/batocera-emulationstation#126).

Changes

• es_export.py: export cached RA game ids to cached_game_ids.txt on every cache mutation (hooked centrally in Storage); read by the EmulationStation integration for the offline icons
• New CLI: cache-roms --paths-file (batch caching with progress output for the ES gamelist action) and export-cached-ids
• knulli_service.py + menu: when the Knulli service is installed, the SDL menu hides Start/Stop, autostart and Uninstall (single control point: ES Services toggle) and shows "KNULLI SERVICE" status; unchanged behavior on muOS/Onion or without the service
• linux/knulli/integration/: dev kit used for on-device testing (service file, configgen patcher with revert, ES deploy scripts)

Fixes

• retroarch_cfg.py: upsert regex could swallow the following config line when a value was empty (\s* matches newlines) — corrupted retroarch.cfg; orphan "" lines are now also self-healed
• batocera_conf.py: revert no longer touches global.retroachievements — the proxy may enable the master toggle but never disables it

Tested on RG40XX-H (h700); tag knulli-native-preview-1 was built from this branch.