rclone: safer restores, RSYNCRMDIR, drop legacy mount code

[maxengel]

Correctness and safety cleanup of the cloud backup/restore tools, squashed to a single commit for review. Docs PR: ROCKNIX/rocknix.org#176.

• Restore can no longer delete local data. The filter rules are an allowlist, so on a RESTOREMETHOD="sync" restore a user-supplied --delete-excluded would delete everything local that isn't a save/state/screenshot (ROMs, BIOS, artwork). It is now stripped during restore option normalization (same pattern as the existing --verbose strip); backup keeps it, where it only tidies the remote. Also removes the dead RESTORE_RCLONEOPTS assignment.
• RSYNCRMDIR actually works now. It shipped enabled and documented on rocknix.org, but no script ever read it. After a successful game-saves backup, cloud_backup prunes empty remote directories via rclone rmdirs --leave-root (non-fatal on failure).
• Legacy pre-cloud_sync code removed: the rclonectl FUSE-mount wrapper and its rsync.conf/rsync-rules.conf (reachable only via manual SSH, no UI entry) plus the post-update block that re-seeded them on every OS update. Existing copies on user storage are left untouched.
• Smaller fixes: rclone exit code 9 reported as "no files transferred" instead of an error; --stats-one-line in the game-saves flows; removal of controller-input regex branches that could never match (quoted patterns were compared literally); cloud_sync_helper now creates the initial config with sed so the multi-line RCLONEOPTS default survives intact.

Verified with tools/pkgcheck (rclone + rocknix packages), bash -n on all touched scripts, and a repo-wide grep for dangling references.

💘 Generated with Crush

[maxengel]

Correction to the description: rclonectl did have one UI reference — EmulationStation's Network Settings "MOUNT CLOUD DRIVE" toggle. A companion emulationstation-next change replaces that toggle with native CLOUD BACKUP / CLOUD RESTORE entries that launch the supported cloud_sync scripts; PR to follow once build-verified. Merging this PR first is safe: the toggle fails silently today only if a user flips it.

[maxengel]

Rebased onto current next. The remaining check failure is only the release-freeze gate: could a maintainer add the bugfix label? This PR is bug-fix material — it closes a restore-side data-loss hazard (--delete-excluded on a sync restore would delete everything outside the saves allowlist), implements the documented-but-inert RSYNCRMDIR, fixes the misreported rclone exit code 9, repairs the multi-line RCLONEOPTS truncation in config creation, and removes dead legacy code that reseeded stale configs on every update.