feat(analytics): replace budget page with spending analytics + split-adjusted amounts

- Rename 'Budget' → 'Analytics' in sidebar
- Rewrite /budget page: summary cards, recharts bar charts (monthly trend + category breakdown), 6-month trend table
- Fix analytics API to count only user's share for split transactions (CASE WHEN ts.share_percent IS NOT NULL THEN amount * share_percent / 100 ELSE amount END)
- Install recharts

package.json

@@ -16,7 +16,8 @@
     "pg": "^8.20.0",
     "prisma": "^7.4.2",
     "react": "19.2.3",
-    "react-dom": "19.2.3"
+    "react-dom": "19.2.3",
+    "recharts": "^3.8.0"
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",