Add BestDays and TopCustomers tables to StatisticPage

[IanTheMitten]

Motivation

• Surface the top-performing dates and students in the Statistic view so operators can quickly see highest revenue days and highest spending customers.
• Ensure these rankings respect the same sampled weekday selection controlled by the existing statistic date-range and seed controls.

Description

• Added helper analytics in src/components/statistic/rankingAnalytics.ts with topDaysByRevenue(transactions, limit) and topCustomers(transactions, students, limit) to compute ranked rows.
• Added UI components src/components/statistic/BestDaysTable.tsx and src/components/statistic/TopCustomersTable.tsx that render the top 10 rows; BestDaysTable shows Date, Weekday, Revenue, Tx Count, and TopCustomersTable shows Student, Grade, Spend, Visits, Avg Spend / Visit.
• Integrated both tables into src/components/statistic/StatisticPage.tsx by computing filteredTransactions from getSampledTransactionDates(...)/getDayKey(...) and rendering the two tables in a two-column grid below the charts.
• Updated src/App.tsx to pass students into StatisticPage so customer names/grades can be resolved in the top customers table.

Testing

• Ran the production build with npm run build, which completed successfully.
• No automated unit tests were added or run as part of this change.

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Codex Task