chore: refactor fronend code

[IvanPartsunev]

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Summary

• Standardize table styling across all pages with pixel-based column widths to prevent column overlap
• Migrate admin pages from manual state management to React Query hooks for better caching
• Add shared style constants and utilities for consistent UI patterns
• Add comprehensive README documentation for frontend directories

Changes

Table Styling Refactor

• Replace percentage-based column widths with pixel values to fix column overlap issues
• Add TABLE_STYLES constants with table size variants (tableSmall, tableMedium, tableLarge, tableXLarge)
• Add COLUMN_WIDTHS constants for consistent column sizing (rowNumber, name, email, phone, actions, etc.)
• Update all table components: Board, Control, CooperativeMembers, Proxies, ProductsManagement, DocumentsManagement, NewsManagement, UserManagement

Caching Improvements

• Migrate admin pages to use React Query hooks instead of manual useState/useEffect
• Add usePagination hook for consistent table pagination logic
• Reduce redundant API calls through query caching

Shared Utilities

• Add lib/tableUtils.ts with table styling constants and pagination helpers
• Add lib/styles.ts with HERO_STYLES and SECTION_STYLES for consistent page layouts

Documentation

• Add README files for components/, hooks/, lib/, and pages/ directories
• Document available utilities, hooks, and component patterns

Bug Fixes

• Fix uploaded_by_name display in DocumentsManagement (was showing ID instead of name)
• Fix TypeScript type issues with optional fields in User, FileMetadata, and NewsItem interfaces
• Add proper null checks for optional date and ID fields

Test plan

• Verify all tables display without column overlap on different screen sizes
• Check horizontal scroll works on narrow viewports
• Verify admin panel caching (navigate away and back - should not refetch)
• Confirm DocumentsManagement shows uploader name, not ID
• Run pnpm build - should complete without TypeScript errors

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