feat(dashboard): optimize teacher dashboard ui and layout

- Refactor layout: move Needs Grading to main column, Homework to sidebar
- Enhance TeacherStats: replace static counts with actionable metrics (Needs Grading, Active Assignments, Avg Score, Submission Rate)
- Update RecentSubmissions: table view with quick grade actions and late status
- Update TeacherSchedule: vertical timeline view with scroll hints
- Update TeacherHomeworkCard: compact list view
- Integrate Recharts: add TeacherGradeTrends chart and shared chart component
- Update documentation

package.json

@@ -46,8 +46,9 @@
     "react-dom": "19.2.1",
     "react-hook-form": "^7.69.0",
     "react-markdown": "^10.1.0",
-    "remark-gfm": "^4.0.1",
+    "recharts": "^3.6.0",
     "remark-breaks": "^4.0.0",
+    "remark-gfm": "^4.0.1",
     "sonner": "^2.0.7",
     "tailwind-merge": "^3.4.0",
     "tailwindcss-animate": "^1.0.7",
@@ -56,8 +57,8 @@
   },
   "devDependencies": {
     "@faker-js/faker": "^10.1.0",
-    "@tailwindcss/typography": "^0.5.16",
     "@tailwindcss/postcss": "^4",
+    "@tailwindcss/typography": "^0.5.16",
     "@types/node": "^20",
     "@types/react": "^19",
     "@types/react-dom": "^19",