fix: production readiness — resolve build, lint, and code quality issues

- Fix Next.js build failure: remove duplicate route at (dashboard)/listings/[id]
  that conflicted with (public)/listings/[id] (same URL path in two route groups)
- Fix 772 ESLint errors: auto-fix import ordering (import-x/order), remove unused
  imports/variables, convert empty interfaces to type aliases, replace require()
  with ESM imports, fix consistent-type-imports violations
- Add CLAUDE.md for developer onboarding documentation
- All checks pass: 0 lint errors, typecheck clean, 230 tests passing, build success

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/components/listings/image-upload.tsx

@@ -1,8 +1,8 @@
 'use client';
 
 import * as React from 'react';
-import { cn } from '@/lib/utils';
 import { Button } from '@/components/ui/button';
+import { cn } from '@/lib/utils';
 
 interface ImageFile {
   file: File;
@@ -79,8 +79,7 @@ export function ImageUpload({ images, onChange, maxFiles = 20, className }: Imag
     return () => {
       images.forEach((img) => URL.revokeObjectURL(img.preview));
     };
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, []);
+  }, []); // intentionally empty: runs only on unmount to revoke object URLs
 
   return (
     <div className={cn('space-y-4', className)}>