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/common/mod.rs

@@ -1,4 +1,4 @@
-pub mod errors;
 pub mod config;
 pub mod di;
-pub mod stubs;
+pub mod errors;
+pub mod stubs;