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/components/home/guest-view.tsx

@@ -1,5 +1,6 @@
 import { getTranslations } from "next-intl/server";
 import Link from "next/link";
+import Image from "next/image";
 import { avatarImageUrl, excerpt } from "@/lib/format";
 import { prisma } from "@/lib/prisma";
 import { siteSettings } from "@/lib/services/site-settings";
@@ -7,7 +8,7 @@ import { HomeLoginForm } from "@/components/auth/home-login-form";
 
 export default async function GuestView() {
   const t = await getTranslations("pages.home");
-  const hotelName = (await siteSettings.get("hotel_name", "Atom")) ?? "Atom";
+  const _hotelName = await siteSettings.get("hotel_name", "Atom");
   const imager =
     (await siteSettings.get("habbo_imaging_url", "https://www.habbo.com/habbo-imaging/avatarimage")) ?? "";
 
@@ -65,7 +66,7 @@ export default async function GuestView() {
 
         <a href="/register" className="relative block">
           <div className="inline-block overflow-hidden rounded-lg border" style={{ borderColor: "color-mix(in srgb, var(--color-text-muted) 22%, transparent)" }}>
-            <img src="/assets/images/EnterHubbly.png" alt="Register" className="block" />
+            <Image src="/assets/images/EnterHubbly.png" alt="Register" width={300} height={100} className="block" unoptimized />
           </div>
           <span
             className="pointer-events-none absolute inset-0 flex items-center text-4xl font-extrabold text-white text-shadow"
@@ -96,21 +97,20 @@ export default async function GuestView() {
                   className="relative overflow-visible rounded-md p-0 shadow-lg"
                   style={{ width: "50px", height: "50px", justifySelf: "center", backgroundColor: "var(--color-surface)" }}
                 >
-                  <img
+                  <Image
                     src={avatarImageUrl(imager, u.look, { headOnly: true, direction: 3 })}
                     alt={u.username}
-                    loading="lazy"
-                    decoding="async"
+                    width={50}
+                    height={62}
                     style={{
                       position: "absolute",
                       top: "-12px",
                       left: "50%",
                       transform: "translateX(-50%)",
-                      width: "auto",
-                      height: "auto",
                       maxWidth: "none",
                       maxHeight: "none",
                     }}
+                    unoptimized
                   />
                 </div>
               ))}
@@ -150,11 +150,12 @@ export default async function GuestView() {
                     }}
                   >
                     <div className="relative h-full w-full overflow-hidden rounded-lg">
-                      <img
+                      <Image
                         src={a.image}
                         alt={a.title}
-                        className="h-full w-full rounded-lg object-cover transition-all duration-300 group-hover:scale-105"
-                        loading="lazy"
+                        fill
+                        className="rounded-lg object-cover transition-all duration-300 group-hover:scale-105"
+                        unoptimized
                       />
                       <div
                         className="absolute left-0 w-full p-2"