feat: page-based pagination for iOS data browser

[datlechin]

Summary

• Replace infinite scroll "Load More" with prev/next page controls
• Bottom toolbar shows: ← Prev | 1-100 of 5,432 | Next →
• Fetches total row count via SELECT COUNT(*)
• Pull-to-refresh reloads current page
• Added SQLBuilder.buildCount() for count queries

Test plan

• Open a table with many rows - pagination bar appears at bottom
• Tap Next - loads next page, rows replaced
• Tap Prev - loads previous page
• Prev disabled on first page
• Next disabled on last page
• Pull-to-refresh reloads current page
• Row count label shows correct range
• Empty table shows no pagination bar