fix: address formatting violations in Rust code
- Fixed function signature line length in get_stored_did_doc (apps/identity-wallet/src-tauri/src/lib.rs:683)
- Fixed .map_err chain formatting (apps/identity-wallet/src-tauri/src/lib.rs:687-690)
- Applied cargo fmt --all to automatically fix all formatting issues
Verified with cargo fmt --all --check (no violations remain)