Implement pagination for participant query

[BassemHalim]

The current participant query implementation fetches all participants without pagination:

egytech-fyi-api/src/routes/participants.ts

Line 36 in 704e8df

const results = await c.env.DB.prepare(`SELECT * FROM participants_d3 ${whereClause}`).all();

While the table is small enough now, this approach may lead to performance issues and excessive memory usage as the number of participants grows. We should implement pagination to ensure the application remains scalable.