Security hardening, code quality, and ESLint setup

- Remove production DB dump (db_backup_*.sql) and update.log from git tracking
- Add DB backups to .gitignore
- Replace all console.log/console.error with structured logger module
- Translate Dutch error messages to English (link-discord.ts)
- Remove dead code blocks (register-form.tsx false && pattern)
- Add ESLint flat config with TypeScript, React, Next.js, jsx-a11y, and security plugins
- Add Prettier config
- Add eslint-plugin-security for security-aware linting
- Fix all 119+ ESLint warnings across the codebase:
  - Resolve security/detect-object-injection with safe access patterns
  - Resolve security/detect-non-literal-fs-filename with path traversal validation
  - Replace <img> with next/image <Image> component
  - Remove unused variables and imports
  - Replace non-null assertions with proper type guards
  - Replace <a> with <Link> for internal navigation
  - Use next/script Script component for external scripts
- Fix setState-in-useEffect anti-patterns (navbar-color-picker, logo-generator, theme-switcher)
- Add lint and format scripts to package.json

All checks: typecheck ✓, tests 58/58 ✓, lint 0 errors 0 warnings ✓

src/app/admin/radio/banners/page.tsx

@@ -6,7 +6,8 @@ import {
 } from '@/actions/admin-radio-extra';
 import { prisma } from '@/lib/prisma';
 import { StatusCard } from '@/components/admin/dashboard';
-import { Image } from 'lucide-react';
+import NextImage from 'next/image';
+import { Image as LucideImage } from 'lucide-react';
 import { getTranslations } from "next-intl/server";
 
 export const dynamic = 'force-dynamic';
@@ -66,7 +67,7 @@ export default async function AdminRadioBannersPage() {
 
       <div className="flex items-center gap-3 mb-6">
         <div className="w-10 h-10 rounded-xl bg-gradient-to-br from-[var(--color-primary)]/20 to-[var(--color-primary)]/5 grid place-items-center">
-          <Image size={20} className="text-[var(--color-primary)]" />
+          <LucideImage size={20} className="text-[var(--color-primary)]" />
         </div>
         <div>
           <h1 className="m-0 text-xl font-extrabold text-[var(--color-text)]">{t("banners.heading")}</h1>
@@ -176,10 +177,13 @@ export default async function AdminRadioBannersPage() {
                 </div>
 
                 {b.imagePath ? (
-                  <img
+                  <NextImage
                     src={b.imagePath}
                     alt={b.title ?? t("banners.bannerAlt")}
+                    width={800}
+                    height={200}
                     className="article-img my-2"
+                    unoptimized
                   />
                 ) : null}