add config-sqlite and http-api adapters

SQLite config store: full ConfigRepository impl with JSON serialization
for mappings, layouts, data source configs. 12 integration tests.

HTTP API: Axum REST endpoints for widgets, data sources, layout, presets.
6 integration tests using tower::oneshot.

Port traits updated to return Send futures for Axum compatibility.

crates/domain/src/ports/event.rs

@@ -1,7 +1,8 @@
+use std::future::Future;
 use crate::events::DomainEvent;
 
 pub trait EventPublisher {
     type Error;
 
-    async fn publish(&self, event: DomainEvent) -> Result<(), Self::Error>;
+    fn publish(&self, event: DomainEvent) -> impl Future<Output = Result<(), Self::Error>> + Send;
 }