fix: resolve Docker build failures and configuration issues

Add missing dependencies, fix Next.js config, update Docker Compose, and configure Tailwind CSS.

#VERCEL_SKIP

Co-authored-by: Anders Lehmann Pier <3219386+AndersPier@users.noreply.github.com>

app/api/health/route.ts

@@ -1,12 +0,0 @@
-import { NextResponse } from "next/server"
-
-export async function GET() {
-  return NextResponse.json(
-    {
-      status: "healthy",
-      timestamp: new Date().toISOString(),
-      service: "markdown-editor",
-    },
-    { status: 200 },
-  )
-}