feat: Display biomarkers by category in collapsible sections on the dashboard, including new UI styles and backend category_id in the API response.

backend/src/handlers/biomarkers.rs

@@ -43,6 +43,7 @@ pub struct ReferenceRuleResponse {
 #[derive(Serialize)]
 pub struct BiomarkerListItem {
     pub id: i32,
+    pub category_id: i32,
     pub name: String,
     pub test_category: String,
     pub unit: String,
@@ -62,6 +63,7 @@ pub async fn list_biomarkers(
         .into_iter()
         .map(|b| BiomarkerListItem {
             id: b.id,
+            category_id: b.category_id,
             name: b.name,
             test_category: b.test_category,
             unit: b.unit,