Fix rustfmt and clippy issues

- Add missing newlines at end of files
- Remove trailing whitespace
- Use next_back() instead of last() for DoubleEndedIterator
- Use &Path instead of &PathBuf for function parameter

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/registry/mod.rs

@@ -87,19 +87,19 @@ impl RegistryClient {
             .context("Failed to push manifest")?;
 
         info!("Successfully pushed image to {}", manifest_url);
-        
+
         // Extract digest from the manifest URL
         // URL format: https://registry/v2/repo/manifests/sha256:digest
         let digest = manifest_url
             .split('/')
-            .last()
+            .next_back()
             .context("Failed to extract digest from manifest URL")?;
-        
+
         // Build the full image reference with digest
         let registry = reference.registry();
         let repository = reference.repository();
         let digest_ref = format!("{}/{}@{}", registry, repository, digest);
-        
+
         Ok(digest_ref)
     }
 }