Add trend charts and calendar-week averages to History page

Adds Recharts-based calorie and macro trend charts plus real
calendar-week (Mon-Sun) averages, replacing the old rolling
7-day average. Colors were chosen and validated with the dataviz
skill's contrast/CVD checks separately for light and dark mode.

Fixes a timezone bug where Date.toISOString() shifted week
boundaries by one day in UTC+ timezones, and two Recharts pitfalls
(negative chart margin hiding the Y-axis, mount animation stuck
invisible in headless browsers).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/package.json

@@ -14,7 +14,8 @@
     "html5-qrcode": "^2.3.8",
     "react": "^19.2.7",
     "react-dom": "^19.2.7",
-    "react-router-dom": "^7.18.1"
+    "react-router-dom": "^7.18.1",
+    "recharts": "^3.10.1"
   },
   "devDependencies": {
     "@tailwindcss/vite": "^4.3.2",