Next.js bug fix in my project

I have an existing Next.js application using TypeScript, Tailwind CSS and Supabase. Several issues have appeared as the application has grown. Issues to investigate and fix: Hydration mismatch on one dashboard page Supabase session occasionally disappears after refresh Search currently sends too many database requests One API endpoint performs unnecessary database queries Mobile dashboard has a responsive layout issue Improve loading/error states without changing the existing UI unnecessarily Requirements: Diagnose the root causes rather than applying temporary workarounds Keep the existing architecture where practical Avoid unnecessary client components Keep existing functionality working Explain the major changes after completion Stack: Next.js, React, TypeScript, Tailwind CSS, Supabase. Please review the existing code before proposing major architectural changes.