Update participant and study API routes

src/components/study/StudySelector.tsx

@@ -0,0 +1,31 @@
+import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "~/components/ui/select";
+import { Study } from '../../types/Study';
+
+interface StudySelectorProps {
+  studies: Study[];
+  selectedStudy: Study | null;
+  onStudyChange: (studyId: string) => void;
+}
+
+export function StudySelector({ studies, selectedStudy, onStudyChange }: StudySelectorProps) {
+  return (
+    <Select onValueChange={onStudyChange} value={selectedStudy?.id?.toString() || ""}>
+      <SelectTrigger className="w-[200px]">
+        <SelectValue placeholder="Select a study" />
+      </SelectTrigger>
+      <SelectContent>
+        {studies.length > 0 ? (
+          studies.map((study) => (
+            <SelectItem key={study.id} value={study.id.toString()}>
+              {study.title}
+            </SelectItem>
+          ))
+        ) : (
+          <SelectItem value="no-studies" disabled className="text-gray-400 italic">
+            No studies available
+          </SelectItem>
+        )}
+      </SelectContent>
+    </Select>
+  );
+}