feat: Add health check endpoint for network status detection

Created /api/health endpoint that returns 200 OK to allow Redux
network detection middleware to properly check connectivity status.

Without this endpoint, the app was showing as offline even when
connected to the internet.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

maternal-web/app/api/health/route.ts

@@ -0,0 +1,13 @@
+import { NextResponse } from 'next/server';
+
+/**
+ * Health check endpoint for network status detection
+ * Returns 200 OK when the app is reachable
+ */
+export async function GET() {
+  return NextResponse.json({ status: 'ok', timestamp: new Date().toISOString() });
+}
+
+export async function HEAD() {
+  return new NextResponse(null, { status: 200 });
+}