feat: wire chain clients into AppState (feature-gated)

Add ChainClients (infra/chains.rs): per-chain data-source handles built once at
startup from config and shared via AppState. Each client is present only when
its chain feature flag is on, and a malformed chain endpoint now fails startup
(fail-closed) rather than the first request. Cloneable (grin's session state is
shared via Arc) so it lives in the cloneable AppState.

Foundation for the wallet-handlers phase — handlers will read these clients
from State. No endpoints yet (openapi unchanged).

src/infra/chains.rs

@@ -0,0 +1,53 @@
+//! Per-chain client handles, constructed once at startup and shared via
+//! [`crate::AppState`]. Each chain's client is config-pointed at an external node
+//! service (Fulcrum/Electrum, monero/wownero-lws, grin-wallet + grin node) and is
+//! present only when that chain's feature flag is enabled. A malformed endpoint
+//! fails startup (fail-closed), not the first request.
+
+use std::sync::Arc;
+
+use crate::config::Config;
+use crate::error::AppError;
+use crate::infra::electrum::ElectrumClient;
+use crate::infra::grin::GrinClient;
+use crate::infra::lws::LwsClient;
+
+/// The enabled chains' data-source clients. Cloneable (the heavyweight grin
+/// session state is shared via `Arc`) so it can live in the cloneable `AppState`.
+#[derive(Clone)]
+pub struct ChainClients {
+    pub btc: Option<ElectrumClient>,
+    pub ltc: Option<ElectrumClient>,
+    pub xmr: Option<LwsClient>,
+    pub wow: Option<LwsClient>,
+    pub grin: Option<Arc<GrinClient>>,
+}
+
+impl ChainClients {
+    /// Build clients for the enabled chains from config.
+    pub fn from_config(cfg: &Config) -> Result<Self, AppError> {
+        let flags = &cfg.features.chains;
+        Ok(Self {
+            btc: flags
+                .btc
+                .then(|| ElectrumClient::bitcoin(&cfg.chains.btc))
+                .transpose()?,
+            ltc: flags
+                .ltc
+                .then(|| ElectrumClient::litecoin(&cfg.chains.ltc))
+                .transpose()?,
+            xmr: flags
+                .xmr
+                .then(|| LwsClient::monero(&cfg.chains.xmr))
+                .transpose()?,
+            wow: flags
+                .wow
+                .then(|| LwsClient::wownero(&cfg.chains.wow))
+                .transpose()?,
+            grin: flags
+                .grin
+                .then(|| GrinClient::new(&cfg.chains.grin).map(Arc::new))
+                .transpose()?,
+        })
+    }
+}

src/infra/mod.rs

@@ -1,6 +1,7 @@
 //! Infrastructure layer: adapters for external services (database, chain nodes,
 //! light-wallet servers). Chain clients are wired in as they land.
 
+pub mod chains;
 pub mod db;
 pub mod electrum;
 pub mod grin;

src/lib.rs

@@ -23,6 +23,7 @@ use tokio::sync::RwLock;
 
 use crate::config::Config;
 use crate::core::session::{SessionManager, WebChallenge};
+use crate::infra::chains::ChainClients;
 use crate::infra::db::Database;
 
 /// Shared application state injected into handlers via `State<Arc<AppState>>`.
@@ -31,6 +32,8 @@ pub struct AppState {
     pub config: Config,
     pub db: Database,
     pub sessions: SessionManager,
+    /// Per-chain data-source clients (present only for enabled chains).
+    pub chains: ChainClients,
     /// In-memory website-auth challenges, keyed by nonce. Single-node store;
     /// a shared/stateless variant is the load-balanced-fleet path.
     pub web_challenges: Arc<RwLock<HashMap<String, WebChallenge>>>,

src/main.rs

@@ -9,7 +9,8 @@ use std::sync::Arc;
 use sqlx::postgres::PgPoolOptions;
 
 use smirk_backend_core::{
-    build_router, config::Config, core::session::SessionManager, infra::db::Database, AppState,
+    build_router, config::Config, core::session::SessionManager, infra::chains::ChainClients,
+    infra::db::Database, AppState,
 };
 
 #[tokio::main]
@@ -33,12 +34,14 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         config.secrets.ip_salt.clone(),
     );
     let sessions = SessionManager::new(&config.auth.jwt_secret, config.auth.jwt_expiry_hours);
+    let chains = ChainClients::from_config(&config)?;
 
     let addr = format!("{}:{}", config.server_host, config.server_port);
     let state = Arc::new(AppState {
         config,
         db,
         sessions,
+        chains,
         web_challenges: Arc::default(),
     });
 

tests/common/mod.rs

@@ -21,7 +21,8 @@ use tower::ServiceExt;
 use uuid::Uuid;
 
 use smirk_backend_core::{
-    build_router, config::Config, core::session::SessionManager, infra::db::Database, AppState,
+    build_router, config::Config, core::session::SessionManager, infra::chains::ChainClients,
+    infra::db::Database, AppState,
 };
 
 static INIT_ENV: Once = Once::new();
@@ -68,10 +69,12 @@ pub async fn try_app() -> Option<TestApp> {
         config.secrets.ip_salt.clone(),
     );
     let sessions = SessionManager::new(&config.auth.jwt_secret, config.auth.jwt_expiry_hours);
+    let chains = ChainClients::from_config(&config).expect("build chain clients");
     let state = Arc::new(AppState {
         config,
         db,
         sessions,
+        chains,
         web_challenges: Arc::default(),
     });