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/components/shared/custom-fields-section.tsx

@@ -1,6 +1,6 @@
 'use client';
 
-import { useCallback, useRef, useState } from 'react';
+import { useRef, useState } from 'react';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { ChevronDown, ChevronRight } from 'lucide-react';
 
@@ -15,7 +15,6 @@ import {
   SelectTrigger,
   SelectValue,
 } from '@/components/ui/select';
-import { Button } from '@/components/ui/button';
 import { apiFetch } from '@/lib/api/client';
 
 // ─── Types ────────────────────────────────────────────────────────────────────