⚡ Optimize keybox backup restore by combining root commands

Combined the check for backup file existence and the move command into a single `su` invocation in `PIFS/AllTargetMagiskhide.sh`. ### 💡 What Modified the backup restore logic to use `su -c "[ -f ... ] && mv ..."` instead of two separate `su -c` calls. ### 🎯 Why Reducing the number of `su` calls minimizes the overhead associated with forking and context switching, leading to faster execution. ### 📊 Measured Improvement A benchmark script mocking `su` with a 0.05s delay showed a reduction in execution time from ~1265 ms to ~662 ms for 10 iterations, representing a ~50% improvement for this code block. --- *PR created automatically by Jules for task [9697690326189327517](https://jules.google.com/task/9697690326189327517) started by @tryigit*