Implement full SaaS template

[Josephat-S]

This pull request significantly upgrades the analytics and dashboard pages in the SaaS Next.js monolith template by introducing new, reusable data visualization components and modernizing the layout and data presentation. The changes focus on improving the user experience with interactive charts, concise metric summaries, and visually appealing representations of key data.

The most important changes are:

New Data Visualization Components:

• Added new reusable components: BarChart, DonutChart, LineChart, and SparkLine for rendering various types of charts and sparklines across the dashboard and analytics pages. These components support dynamic data and customizable styles. [1] [2]

Dashboard Page Enhancements (app/page.tsx):

• Replaced static metric cards with dynamic cards that include sparklines, color indicators, and concise trend information. [1] [2]
• Upgraded the revenue overview section by replacing the old bar chart with a new interactive line chart and summary stats, and added quick filter buttons (7D, 30D, 90D, 12M).
• Introduced new sections for "Revenue by Source" (DonutChart) and "Monthly Active Users" (BarChart) for a more comprehensive overview.

Analytics Page Enhancements (app/analytics/page.tsx):

• Revamped the summary metrics row to use dynamic cards with sparklines and trend indicators for key metrics. [1] [2]
• Added a new "Traffic Over Time" section using the LineChart component for visualizing daily traffic trends.
• Updated "Traffic Sources" and "Top Pages" to use the new DonutChart and BarChart components, improving clarity and visual appeal. [1] [2]
• Redesigned the conversion funnel visualization for improved readability and modern styling. [1] [2]

These changes modernize the analytics and dashboard interfaces, making them more interactive, visually appealing, and easier to interpret at a glance.

Closes #35