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/Cargo.toml

@@ -7,6 +7,8 @@ edition = "2024"
 domain.workspace = true
 thiserror.workspace = true
 tokio.workspace = true
+anyhow.workspace = true
+tracing.workspace = true
 
 [dev-dependencies]
 tokio = { workspace = true }