chore: initialize autoresearch baseline

crates/api-contracts/src/health.rs

@@ -0,0 +1,9 @@
+use serde::Serialize;
+
+#[derive(Debug, Clone, Serialize)]
+pub struct HealthResponse {
+    pub status: &'static str,
+    pub model_loaded: bool,
+    pub model_id: Option<String>,
+    pub uptime_secs: u64,
+}