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/domain-sharding/meta.json

@@ -0,0 +1,44 @@
+{
+  "slug": "domain-sharding",
+  "name": "Domain Sharding",
+  "description": "",
+  "tags": [
+    "DNS解析",
+    "DNS配置",
+    "HTML",
+    "HTTP/2",
+    "TCP连接",
+    "TLS",
+    "前端实现",
+    "域名分片",
+    "域名分片淘汰",
+    "多路复用",
+    "子域名",
+    "子域名数量",
+    "并行连接",
+    "性能开销",
+    "最佳实践",
+    "服务器",
+    "服务器部署",
+    "浏览器限制",
+    "缓存碎片化",
+    "计算"
+  ],
+  "difficulty_range": [
+    1,
+    3
+  ],
+  "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
+    }
+  }
+}