Add Qingdao to the tradable city network

Qingdao needs the same airport-settlement path as the other Wunderground-backed APAC cities, so the registry, aliases, timezone, prewarm, official links, market focus, and tests now point to ZSQD / Qingdao Jiaodong International Airport.

Constraint: User supplied Wunderground Qingdao/ZSQD settlement URL.
Rejected: Add a partial registry-only entry | it would show in APIs without frontend links, prewarm coverage, or alias support.
Confidence: high
Scope-risk: narrow
Reversibility: clean
Tested: pytest tests/test_country_networks.py tests/test_web_observability.py::test_cities_endpoint_includes_new_wunderground_cities -q
Tested: npm run build
Not-tested: Live Wunderground fetch for ZSQD in production.

src/data_collection/weather_sources.py

@@ -54,6 +54,7 @@ class WeatherDataCollector(OpenMeteoCacheMixin, SettlementSourceMixin, MetarSour
         "chengdu": ["ZUUU", "ZUTF"],
         "chongqing": ["ZUCK", "ZUPS"],
         "guangzhou": ["ZGGG", "ZGSZ"],
+        "qingdao": ["ZSQD"],
         "shenzhen": ["ZGSZ", "ZGGG"],
         "beijing": ["ZBAA", "ZBAD"],
         "wuhan": ["ZHHH", "ZHES"],
@@ -600,6 +601,9 @@ class WeatherDataCollector(OpenMeteoCacheMixin, SettlementSourceMixin, MetarSour
             "重庆": "Chongqing",
             "shenzhen": "Shenzhen",
             "深圳": "Shenzhen",
+            "qingdao": "Qingdao",
+            "青岛": "Qingdao",
+            "青島": "Qingdao",
             "beijing": "Beijing",
             "北京": "Beijing",
             "wuhan": "Wuhan",