⚡ Improve performance by batching root commands in keybox update

💡 **What:** Batched the `mkdir -p` command and the subsequent conditional backup logic (`if [ -f ... ]; then mv ...; fi`) into a single `su -c sh` session using a piped block. 🎯 **Why:** To reduce process creation overhead associated with invoking `su` multiple times on Android. Each `su` call spawns a new process and context, which is expensive. 📊 **Measured Improvement:** Created a benchmark script `bench.sh` simulating `su` overhead with a 10ms delay. - **Baseline:** ~54ms (3 `su` calls) - **Optimized:** ~27ms (1 `su` call) - **Improvement:** ~50% reduction in wall clock time in the simulated environment. Verified syntax with `bash -n`. --- *PR created automatically by Jules for task [13022275925596462014](https://jules.google.com/task/13022275925596462014) started by @tryigit*