style: apply cargo fmt formatting to existing codebase

Run `cargo fmt` across all Rust source files to enforce consistent
formatting (import ordering, line wrapping, match arm braces).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/domain/repositories/folder_repository.rs

@@ -102,9 +102,5 @@ pub trait FolderRepository: Send + Sync + 'static {
 
     /// Creates a root-level home folder for a user.
     /// This is used during user registration to create the user's personal folder.
-    async fn create_home_folder(
-        &self,
-        user_id: &str,
-        name: String,
-    ) -> Result<Folder, DomainError>;
+    async fn create_home_folder(&self, user_id: &str, name: String) -> Result<Folder, DomainError>;
 }