feat: add Lightning payment endpoints for paid marketplace

- marketplace.create-invoice: generates BOLT11 via LND for app purchase
- marketplace.check-payment: checks invoice settlement status
- Uses existing LND integration (createinvoice/lookupinvoice)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

core/archipelago/src/api/rpc/marketplace.rs

@@ -125,4 +125,77 @@ impl RpcHandler {
             "trust_tier": trust_tier,
         }))
     }
+
+    /// marketplace.create-invoice — Generate a Lightning invoice for app purchase.
+    /// Returns BOLT11 invoice string and payment hash.
+    pub(super) async fn handle_marketplace_create_invoice(
+        &self,
+        params: Option<serde_json::Value>,
+    ) -> Result<serde_json::Value> {
+        let params = params.ok_or_else(|| anyhow::anyhow!("Missing params"))?;
+        let app_id = params
+            .get("app_id")
+            .and_then(|v| v.as_str())
+            .ok_or_else(|| anyhow::anyhow!("Missing app_id"))?;
+        let amount_sats = params
+            .get("amount_sats")
+            .and_then(|v| v.as_u64())
+            .ok_or_else(|| anyhow::anyhow!("Missing amount_sats"))?;
+
+        // Create LND invoice via the existing wallet integration
+        let invoice_params = serde_json::json!({
+            "amount": amount_sats,
+            "memo": format!("Archipelago app: {}", app_id),
+        });
+        let invoice_result = self
+            .handle_lnd_createinvoice(Some(invoice_params))
+            .await?;
+
+        let payment_request = invoice_result
+            .get("payment_request")
+            .and_then(|v| v.as_str())
+            .unwrap_or("");
+        let r_hash = invoice_result
+            .get("r_hash")
+            .and_then(|v| v.as_str())
+            .unwrap_or("");
+
+        Ok(serde_json::json!({
+            "app_id": app_id,
+            "amount_sats": amount_sats,
+            "payment_request": payment_request,
+            "r_hash": r_hash,
+        }))
+    }
+
+    /// marketplace.check-payment — Check if a Lightning payment has been received.
+    pub(super) async fn handle_marketplace_check_payment(
+        &self,
+        params: Option<serde_json::Value>,
+    ) -> Result<serde_json::Value> {
+        let params = params.ok_or_else(|| anyhow::anyhow!("Missing params"))?;
+        let r_hash = params
+            .get("r_hash")
+            .and_then(|v| v.as_str())
+            .ok_or_else(|| anyhow::anyhow!("Missing r_hash"))?;
+
+        // Check invoice status via LND
+        let lookup_params = serde_json::json!({ "r_hash": r_hash });
+        let lookup_result = self
+            .handle_lnd_lookupinvoice(Some(lookup_params))
+            .await;
+
+        let paid = match lookup_result {
+            Ok(ref inv) => inv
+                .get("settled")
+                .and_then(|v| v.as_bool())
+                .unwrap_or(false),
+            Err(_) => false,
+        };
+
+        Ok(serde_json::json!({
+            "r_hash": r_hash,
+            "paid": paid,
+        }))
+    }
 }

core/archipelago/src/api/rpc/mod.rs

@@ -560,6 +560,8 @@ impl RpcHandler {
             "marketplace.get-manifest" => self.handle_marketplace_get_manifest(params).await,
             "marketplace.list-published" => self.handle_marketplace_list_published().await,
             "marketplace.verify" => self.handle_marketplace_verify(params).await,
+            "marketplace.create-invoice" => self.handle_marketplace_create_invoice(params).await,
+            "marketplace.check-payment" => self.handle_marketplace_check_payment(params).await,
 
             // Mesh networking
             "mesh.status" => self.handle_mesh_status().await,