Consolidate global routes into study-scoped architecture

Removed global participants, trials, and analytics routes. All entity
management now flows through study-specific routes. Updated navigation,
breadcrumbs, and forms. Added helpful redirect pages for moved routes.
Eliminated duplicate table components and unified navigation patterns.
Fixed dashboard route structure and layout inheritance.

src/app/(dashboard)/participants/page.tsx

@@ -1,10 +1,65 @@
-import { ParticipantsDataTable } from "~/components/participants/participants-data-table";
-import { StudyGuard } from "~/components/dashboard/study-guard";
+"use client";
+
+import { useEffect } from "react";
+import { useRouter } from "next/navigation";
+import Link from "next/link";
+import { Users, ArrowRight } from "lucide-react";
+import { Button } from "~/components/ui/button";
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardHeader,
+  CardTitle,
+} from "~/components/ui/card";
+import { useStudyContext } from "~/lib/study-context";
+
+export default function ParticipantsRedirect() {
+  const router = useRouter();
+  const { selectedStudyId } = useStudyContext();
+
+  useEffect(() => {
+    // If user has a selected study, redirect to study participants
+    if (selectedStudyId) {
+      router.replace(`/studies/${selectedStudyId}/participants`);
+    }
+  }, [selectedStudyId, router]);
 
-export default function ParticipantsPage() {
   return (
-    <StudyGuard>
-      <ParticipantsDataTable />
-    </StudyGuard>
+    <div className="flex min-h-[60vh] items-center justify-center p-4">
+      <Card className="w-full max-w-md">
+        <CardHeader className="text-center">
+          <div className="mx-auto mb-4 flex h-16 w-16 items-center justify-center rounded-full bg-green-50">
+            <Users className="h-8 w-8 text-green-500" />
+          </div>
+          <CardTitle className="text-2xl">Participants Moved</CardTitle>
+          <CardDescription>
+            Participant management is now organized by study for better
+            organization.
+          </CardDescription>
+        </CardHeader>
+        <CardContent className="space-y-4">
+          <div className="text-muted-foreground space-y-2 text-center text-sm">
+            <p>To manage participants:</p>
+            <ul className="space-y-1 text-left">
+              <li>• Select a study from your studies list</li>
+              <li>• Navigate to that study&apos;s participants page</li>
+              <li>• Add and manage participants for that specific study</li>
+            </ul>
+          </div>
+          <div className="flex flex-col gap-2 pt-4">
+            <Button asChild className="w-full">
+              <Link href="/studies">
+                <ArrowRight className="mr-2 h-4 w-4" />
+                Browse Studies
+              </Link>
+            </Button>
+            <Button asChild variant="outline" className="w-full">
+              <Link href="/dashboard">Go to Dashboard</Link>
+            </Button>
+          </div>
+        </CardContent>
+      </Card>
+    </div>
   );
 }