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/city_time.py

@@ -50,6 +50,7 @@ CITY_TIME_ZONES = {
     "new york": "America/New_York",
     "panama city": "America/Panama",
     "paris": "Europe/Paris",
+    "qingdao": "Asia/Shanghai",
     "san francisco": "America/Los_Angeles",
     "sao paulo": "America/Sao_Paulo",
     "seattle": "America/Los_Angeles",