feat(commands): add battery, gpu, power, and status command implementations

Added full command implementations for battery limit/status, GPU management (cache operations, mode switching, NVIDIA handling), and a status reporter that prints GPU mode and battery details. Introduced module registration and placeholder power command.

New Features
- Battery command support (`limit`, `status`)
- GPU command suite (`cache-delete`, `cache-query`, `reset`, `reset-sddm`, `integrated`, `hybrid`, `nvidia`)
- Status command output showing GPU mode and battery information
- Power command placeholder scaffold

Enhancements
- Unified command registration via `mod.rs`
- Added root checks and file utilities for cache and config operations
- Integrated logging infrastructure

Bug Fixes: none

src/commands/mod.rs

@@ -0,0 +1,4 @@
+pub mod battery;
+pub mod gpu;
+pub mod power;
+pub mod status;