feat: Settings page, DELETE traces endpoint, Anthropic SDK, dashboard bug fixes

- Add /dashboard/settings with SDK connection details, data stats, purge
- Add DELETE /api/traces/[id] with cascade deletion
- Add Anthropic integration (wrap_anthropic) for Python SDK
- Fix missing root duration (totalDuration -> durationMs mapping)
- Fix truncated JSON in decision tree nodes (extract readable labels)
- Fix hardcoded 128K maxTokens in token gauge (model-aware context windows)
- Enable Settings nav item in sidebar

apps/web/src/app/api/settings/stats/route.ts

@@ -0,0 +1,25 @@
+import { NextResponse } from "next/server";
+import { prisma } from "@/lib/prisma";
+
+export async function GET() {
+  try {
+    const [totalTraces, totalSpans, totalDecisions, totalEvents] =
+      await Promise.all([
+        prisma.trace.count(),
+        prisma.span.count(),
+        prisma.decisionPoint.count(),
+        prisma.event.count(),
+      ]);
+
+    return NextResponse.json(
+      { totalTraces, totalSpans, totalDecisions, totalEvents },
+      { status: 200 }
+    );
+  } catch (error) {
+    console.error("Error fetching stats:", error);
+    return NextResponse.json(
+      { error: "Internal server error" },
+      { status: 500 }
+    );
+  }
+}