arch: split ConfigRepository, extract polling, consolidate conversions, decouple protocol

- Value↔JSON: From impls on domain Value behind `json` feature, delete 4 duplicate converters
- ConfigRepository split into ConfigRepository (12), UserRepository (3), WidgetStateCache (2)
- polling orchestration moved from bootstrap to application::polling_service
- WidgetRenderer in client-domain owns scroll/cache, both clients use it
- network loop consolidated into client-application::run_connection_loop
- protocol crate drops domain dep, Wire↔Domain conversions move to adapters

crates/adapters/config-sqlite/tests/config_store_tests.rs

@@ -2,7 +2,7 @@ use config_sqlite::SqliteConfigStore;
 use domain::{
     AlignItems, ConfigRepository, ContainerNode, DataSource, DataSourceConfig, DataSourceType,
     Direction, DisplayHint, DisplayHintKind, JustifyContent, KeyMapping, Layout, LayoutChild,
-    LayoutNode, LayoutPreset, Sizing, WidgetConfig,
+    LayoutNode, LayoutPreset, Sizing, UserRepository, WidgetConfig, WidgetStateCache,
 };
 use std::time::Duration;