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/application/src/auth_service.rs

@@ -1,4 +1,4 @@
-use domain::{AuthPort, ConfigRepository, PasswordHashPort, User};
+use domain::{AuthPort, PasswordHashPort, User, UserRepository};
 
 pub enum AuthError<E> {
     InvalidCredentials,
@@ -26,7 +26,7 @@ pub async fn login<C, A, H>(
     password: &str,
 ) -> Result<String, AuthError<C::Error>>
 where
-    C: ConfigRepository,
+    C: UserRepository,
     A: AuthPort,
     H: PasswordHashPort,
 {
@@ -55,7 +55,7 @@ pub async fn register<C, H>(
     password: &str,
 ) -> Result<(), AuthError<C::Error>>
 where
-    C: ConfigRepository,
+    C: UserRepository,
     H: PasswordHashPort,
 {
     let count = config.count_users().await.map_err(AuthError::Repository)?;