fix: improve error handling and type safety

- Replaced 'any' types with proper TypeScript types
- Improved error handling with instanceof checks
- Removed unused imports (calculateExpectedTeamScore)
- Updated error messages to be more descriptive
- Removed deprecated eslint.config.mjs file

src/app/admin/tournaments/new/page.tsx

@@ -150,8 +150,9 @@ export default function NewTournamentPage() {
 
       // Redirect to game entry page
       router.push(`/admin/tournaments/${tournamentId}/entry`)
-    } catch (err: any) {
-      setError(err.message)
+    } catch (err: unknown) {
+      const message = err instanceof Error ? err.message : "An unexpected error occurred";
+      setError(message)
     } finally {
       setIsLoading(false)
     }