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/lib/services/alert.ts

@@ -1,6 +1,7 @@
 import { prisma } from "@/lib/prisma";
 import { sendMail } from "@/lib/services/email";
 import { env } from "@/env";
+import { logger } from "@/lib/logger";
 
 // === Alert service (AtomCMS → Next.js) ===========================================
 //
@@ -111,12 +112,12 @@ async function postDiscord(input: SendAlertInput): Promise<boolean> {
       body: JSON.stringify(body),
     });
     if (!res.ok) {
-      console.error("[alert] Discord webhook returned", res.status);
+      logger.error("Discord webhook returned non-OK status", { module: "alert", status: res.status });
       return false;
     }
     return true;
   } catch (e) {
-    console.error("[alert] Discord webhook failed:", (e as Error).message);
+    logger.error("Discord webhook failed", { module: "alert", error: (e as Error).message });
     return false;
   }
 }
@@ -152,7 +153,7 @@ async function emailStaff(input: SendAlertInput): Promise<boolean> {
   try {
     return await sendMail(to, subject, html);
   } catch (e) {
-    console.error("[alert] staff email failed:", (e as Error).message);
+    logger.error("Staff email failed", { module: "alert", error: (e as Error).message });
     return false;
   }
 }
@@ -189,7 +190,7 @@ export async function sendAlert(input: SendAlertInput): Promise<SendAlertResult>
   } catch (e) {
     // DB unreachable / schema drift: keep the alert best-effort. We already
     // notified Discord/email above, so the alert isn't lost.
-    console.error("[alert] failed to persist alert_logs row:", (e as Error).message);
+    logger.error("Failed to persist alert_logs row", { module: "alert", error: (e as Error).message });
   }
 
   return { logged, sentViaDiscord, sentViaEmail };