refactor: replace hardcoded hex colors with theme tokens, move data/ to root

- Add --color-green-mid token (#4a7a55) to @theme for dimmer stat values
- Replace all text-[#hex]/bg-[#hex] arbitrary values with named tokens:
  text-green, text-green-light, text-green-sec, text-green-muted,
  text-green-dark, text-green-mid, text-text, bg-card, bg-bg, border-border
- Replace rgba(34,197,94,X) inline styles with bg-green/X opacity modifiers
- Convert single-prop style={{ borderColor/background }} to className
- Fix SVG stroke="#dff5e8" → stroke="currentColor"
- Use CSS variables in globals.css base styles (background-color, color)
- Move app/data/wikipedia/ → data/ (project root, not inside Next.js app dir)
- Update Dockerfile, seed.ts, scrape-wikipedia.ts paths accordingly
- Remove unused app/data/world_cup.csv

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

data/2018/worldcup.groups.json

@@ -0,0 +1,76 @@
+{
+  "groups": [
+    {
+      "name": "Group A",
+      "teams": [
+        "Russia",
+        "Saudi Arabia",
+        "Egypt",
+        "Uruguay"
+      ]
+    },
+    {
+      "name": "Group B",
+      "teams": [
+        "Morocco",
+        "Iran",
+        "Portugal",
+        "Spain"
+      ]
+    },
+    {
+      "name": "Group C",
+      "teams": [
+        "France",
+        "Australia",
+        "Peru",
+        "Denmark"
+      ]
+    },
+    {
+      "name": "Group D",
+      "teams": [
+        "Argentina",
+        "Iceland",
+        "Croatia",
+        "Nigeria"
+      ]
+    },
+    {
+      "name": "Group E",
+      "teams": [
+        "Costa Rica",
+        "Serbia",
+        "Brazil",
+        "Switzerland"
+      ]
+    },
+    {
+      "name": "Group F",
+      "teams": [
+        "Germany",
+        "Mexico",
+        "Sweden",
+        "South Korea"
+      ]
+    },
+    {
+      "name": "Group G",
+      "teams": [
+        "Belgium",
+        "Panama",
+        "Tunisia",
+        "England"
+      ]
+    },
+    {
+      "name": "Group H",
+      "teams": [
+        "Colombia",
+        "Japan",
+        "Poland",
+        "Senegal"
+      ]
+    }
+  ]
+}