feat: add 180 questions (90 sc + 90 fb) for networking subtopics

Cover 9 subtopics from the computer networking documentation:
- http-handshake: TCP/TLS/HTTP2/HTTP3 handshakes
- http-connection-cost: connection resource overhead & million concurrency
- connection-pooling: pool reuse, HTTP/1.1 vs HTTP/2
- http-keepalive: Keep-Alive principle, head-of-line blocking
- keepalive-scenarios: when to enable/disable Keep-Alive
- domain-sharding: HTTP/1.1 hack, HTTP/2 obsolescence
- cdn: edge nodes, caching, DDoS protection
- cors: same-origin policy, preflight requests
- go-build-strip: -s -w flags, binary size optimization

topics/networking/cors/meta.json

@@ -0,0 +1,43 @@
+{
+  "slug": "cors",
+  "name": "Cors",
+  "description": "",
+  "tags": [
+    "Access-Control-Allow-Credentials",
+    "CORS",
+    "CSRF",
+    "Cookie",
+    "Nginx",
+    "OPTIONS",
+    "Origin",
+    "Vite",
+    "WebSocket",
+    "反向代理",
+    "同源策略",
+    "安全",
+    "开发代理",
+    "开发环境",
+    "浏览器安全",
+    "简单请求",
+    "跨域",
+    "跨源请求",
+    "预检请求"
+  ],
+  "difficulty_range": [
+    2,
+    4
+  ],
+  "schema_version": "1.0.0",
+  "updated": "2026-09-02",
+  "question_files": [
+    "single_choice",
+    "fill_blank"
+  ],
+  "stats": {
+    "total": 20,
+    "by_type": {
+      "single_choice": 10,
+      "fill_blank": 10
+    }
+  }
+}