Add Analytics Dashboard to Lovable App

Add an analytics dashboard to my Lovable app.

REQUIREMENTS:
1. Create an /analytics page (protected, admin-only or available to all authenticated users).
2. Add a date range picker at the top (Last 7 days, Last 30 days, Last 90 days, Custom range).
3. Display 4 KPI cards at the top: primary metric value, percentage change vs previous period, and trend arrow (up green, down red).
4. Add a line chart showing the primary metric over time using Recharts. Include a tooltip on hover showing exact values.
5. Add a bar chart comparing categories or segments.
6. Add a data table below the charts showing detailed records with pagination.
7. All data fetched from Supabase with the date range applied as a filter.
8. Add a refresh button and auto-refresh every 5 minutes.
9. Loading skeletons while data is being fetched.

DATABASE:
- No new tables. Aggregates data from existing tables.
- Consider creating a Supabase View or RPC function for complex aggregations.

SECURITY:
- Protect the analytics page behind authentication.
- Aggregate data appropriately — don't expose individual user data in shared dashboards.