fix: fedimint --bitcoind-url CLI arg + data-dir

fedimintd v0.10.0 requires --data-dir and --bitcoind-url as CLI args,
not just env vars. Container was exiting with usage error.

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

core/archipelago/src/api/rpc/package/config.rs

@@ -673,7 +673,11 @@ pub(super) async fn get_app_config(
                 format!("FM_BITCOIND_URL=http://{}:8332", host_ip),
             ],
             None,
-            None,
+            Some(vec![
+                "--data-dir".to_string(),
+                "/data".to_string(),
+                format!("--bitcoind-url=http://{}:{}@bitcoin-knots:8332", rpc_user, rpc_pass),
+            ]),
         ),
         "fedimint-gateway" => (
             vec!["8176:8176".to_string(), "9737:9737".to_string()],