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/1970/worldcup.stadiums.json

@@ -0,0 +1,24 @@
+{
+  "stadiums": [
+    {
+      "name": "Estadio Azteca",
+      "city": "Mexico City"
+    },
+    {
+      "name": "Estadio Luis Dosal",
+      "city": "Toluca"
+    },
+    {
+      "name": "Estadio Jalisco",
+      "city": "Guadalajara"
+    },
+    {
+      "name": "Estadio Nou Camp",
+      "city": "León"
+    },
+    {
+      "name": "Estadio Cuauhtémoc",
+      "city": "Puebla"
+    }
+  ]
+}