feat(apps): add unit tests for providers + bind-production + cms config

web-next: bindAllProduction calls all 4 feature binders exactly once;
Providers renders children. web-tanstack: equivalent providers + bind tests.
cms: payload.config exports a SanitizedConfig with all expected collections.

Spec: §6.7, §9

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web-next/src/app/providers.test.tsx

@@ -0,0 +1,14 @@
+import { describe, it, expect } from "vitest";
+import { render, screen } from "@testing-library/react";
+import { Providers } from "./providers";
+
+describe("Providers", () => {
+  it("renders children", () => {
+    render(
+      <Providers>
+        <div data-testid="child">hi</div>
+      </Providers>,
+    );
+    expect(screen.getByTestId("child")).toBeInTheDocument();
+  });
+});