feat: Build Attendance Overview Page

[rakshitjain23]

The "Attendance Overview" page is currently a placeholder. This page should provide a comprehensive summary of the user's attendance for all subjects, pulling data from the Google Sheet. This task depends on the completion of the data persistence issue.

✅ Acceptance Criteria

• Fetch Data: Retrieve all subject and attendance data from the user's Google Sheet.
• Calculate Statistics: For each subject, calculate:
  • Total classes, classes attended, and current attendance percentage.
  • Number of classes the user can safely miss.
  • Number of classes the user must attend to reach their goal.
• Design Subject Card UI: Create a responsive card component displaying the subject name, a progress bar/chart (e.g., green for safe, red for danger), and key stats.
• Layout Page: Arrange the subject cards in a clean, responsive grid or list.

💻 Tech Stack & Guidelines

• Use Tailwind CSS for styling, consistent with the app's dark theme and gradient.
• Use Framer Motion to add subtle loading or transition animations.
• Ensure the UI is fully responsive on both desktop and mobile.