rewire bootstrap with SQLite, HTTP API, and real polling

bootstrap: SQLite config, HTTP API on :3000, TCP on :2699, poll loops.
http-api: added serve() so bootstrap doesn't depend on axum directly.
polling: reads data sources from config, polls via http-json adapter,
pushes changed widgets to connected clients.

configure via API, e.g.:
  curl -X POST localhost:3000/api/data-sources -H 'Content-Type: application/json' -d '{...}'
  curl -X PUT localhost:3000/api/layout -H 'Content-Type: application/json' -d '{...}'

crates/adapters/rss/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2024"
 [dependencies]
 domain.workspace = true
 reqwest.workspace = true
-quick-xml = { version = "0.37", features = ["serialize"] }
+quick-xml = { version = "0.40", features = ["serialize"] }
 serde.workspace = true
 thiserror.workspace = true