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/1954/worldcup.stadiums.json

@@ -0,0 +1,28 @@
+{
+  "stadiums": [
+    {
+      "name": "Charmilles Stadium",
+      "city": "Geneva"
+    },
+    {
+      "name": "Stade Olympique de la Pontaise",
+      "city": "Lausanne"
+    },
+    {
+      "name": "Wankdorf Stadium",
+      "city": "Bern"
+    },
+    {
+      "name": "Hardturm Stadium",
+      "city": "Zürich"
+    },
+    {
+      "name": "St. Jakob Stadium",
+      "city": "Basel"
+    },
+    {
+      "name": "Cornaredo Stadium",
+      "city": "Lugano"
+    }
+  ]
+}