Fix all ESLint errors: remove unused imports, replace any types

- Remove ~60 unused imports and variables across 88 files
- Replace ~80 `any` type annotations with proper types (unknown,
  Record<string, unknown>, or specific types)
- Prefix unused callback args with underscore
- Fix unescaped JSX entities
- Lint now passes cleanly (0 errors, 2 intentional img warnings)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/app/api/v1/expenses/export/csv/route.ts

@@ -1,7 +1,6 @@
 import { NextResponse } from 'next/server';
 
 import { withAuth, withPermission } from '@/lib/api/helpers';
-import { parseBody } from '@/lib/api/route-helpers';
 import { errorResponse } from '@/lib/errors';
 import { exportCsv } from '@/lib/services/expense-export';
 import { listExpensesSchema } from '@/lib/validators/expenses';