feat(settings): Settings1 стаб + атомарный стор + seed дефолтов

Store (load_or_seed/get/set/reset/list, durable-write) + SettingsService #[interface] + bin.
v0: строковые значения (variant на проводе), сам сеет дефолты.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Alexander <akotenev2003@gmail.com>

crates/core/shturman-settings/src/lib.rs

@@ -0,0 +1,7 @@
+//! `ru.shturman.Settings1` — стаб конфигурации (домен Settings/State, architecture §3).
+
+pub mod service;
+pub mod store;
+
+pub use service::SettingsService;
+pub use store::Store;