fix: improve TypeScript types for better IDE code hinting

- Install @types/bun and @types/jsdom for proper type definitions
- Fix mock function typing in test files
- Create jest-dom.d.ts to properly extend Bun's Matchers interface
- Remove MockedFunction imports (not supported in Bun's types)
- Cast global.fetch and useSession mocks to any where needed
- Fix mock.module return types to match expected signatures

This resolves TypeScript errors that were preventing proper code
completion and type checking in IDEs.

src/__tests__/EditTournamentForm.test.tsx

@@ -1,4 +1,4 @@
-import { describe, it, expect, mock, beforeEach, MockedFunction } from 'bun:test'
+import { describe, it, expect, mock, beforeEach } from 'bun:test'
 import { render, screen, waitFor } from '@testing-library/react'
 import userEvent from '@testing-library/user-event'
 import EditTournamentForm from '@/components/EditTournamentForm'
@@ -18,8 +18,8 @@ mock.module('next/link', () => ({
 }))
 
 // Mock fetch
-const mockFetch = mock(() => {})
-global.fetch = mockFetch as MockedFunction<typeof global.fetch>
+const mockFetch = mock(async () => new Response())
+global.fetch = mockFetch as any
 
 const mockTournament = {
   id: 1,