style: apply cargo fmt to entire codebase

Standardize code formatting across all 173 Rust source files
using rustfmt. No functional changes - purely cosmetic.

This establishes a consistent code style baseline for the
project going forward.

src/application/ports/cache_ports.rs

@@ -8,10 +8,10 @@
 //! The application and interface layers remain independent of the caching
 //! implementation details.
 
-use std::path::{Path, PathBuf};
+use crate::common::errors::DomainError;
 use async_trait::async_trait;
 use bytes::Bytes;
-use crate::common::errors::DomainError;
+use std::path::{Path, PathBuf};
 
 /// Statistics for monitoring write-behind cache status.
 #[derive(Debug, Clone, Default)]