fix: retry failed group subpages, add rate-limit detection in scraper

- Detect Wikipedia plain-text rate-limit response ("You are making too many
  requests") and wait 30s before retrying, rather than silently failing
- Increase inter-attempt delay from 3s to 15s per attempt
- Increase group subpage delay from 1.2s to 3s, year delay from 0.6s to 2s
- Re-scrape 1982, 1998, 2002, 2006 which had failed groups; all groups now
  complete — e.g. 2002 now has 64 matches including Group E (Germany/Klose)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

data/1978/worldcup.stadiums.json

@@ -24,6 +24,14 @@
       "name": "Estadio Olímpico Chateau Carreras",
       "city": "Córdoba"
     },
+    {
+      "name": "Estadio José Amalfitani",
+      "city": "Buenos Aires"
+    },
+    {
+      "name": "Estadio José Maria Minella",
+      "city": "Mar del Plata"
+    },
     {
       "name": "Chateau Carreras",
       "city": "Córdoba"