refactor: rename data/openfootball → data/wikipedia, drop data/kaggle

Move world_cup.csv to app/data/ directly (the only remaining Kaggle file
used by seed.ts for tournament metadata). Delete the rest of the Kaggle CSVs.
Update path constants in scrape-wikipedia.ts and seed.ts accordingly.

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

app/data/wikipedia/2006/worldcup.stadiums.json

@@ -0,0 +1,52 @@
+{
+  "stadiums": [
+    {
+      "name": "Allianz Arena",
+      "city": "Munich"
+    },
+    {
+      "name": "Zentralstadion",
+      "city": "Leipzig"
+    },
+    {
+      "name": "Gottlieb-Daimler-Stadion",
+      "city": "Stuttgart"
+    },
+    {
+      "name": "Frankenstadion",
+      "city": "Nuremberg"
+    },
+    {
+      "name": "Fritz-Walter-Stadion",
+      "city": "Kaiserslautern"
+    },
+    {
+      "name": "RheinEnergieStadion",
+      "city": "Cologne"
+    },
+    {
+      "name": "Westfalenstadion",
+      "city": "Dortmund"
+    },
+    {
+      "name": "Niedersachsenstadion",
+      "city": "Hanover"
+    },
+    {
+      "name": "Olympiastadion",
+      "city": "Berlin"
+    },
+    {
+      "name": "Volksparkstadion",
+      "city": "Hamburg"
+    },
+    {
+      "name": "Arena AufSchalke",
+      "city": "Gelsenkirchen"
+    },
+    {
+      "name": "Waldstadion",
+      "city": "Frankfurt"
+    }
+  ]
+}