refactor: convert repository to monorepo with npm workspaces

Restructured the repository into a monorepo to better organize application code
and maintenance scripts.

## Workspace Structure
- web-app: Next.js application (all app code moved from root)
- housekeeping: Database backup and maintenance scripts

## Key Changes
- Moved all application code to web-app/ using git mv
- Moved database scripts to housekeeping/ workspace
- Updated Dockerfile for monorepo build process
- Updated docker-compose files (volume paths: ./web-app/etc/hosts/)
- Updated .gitignore for workspace-level node_modules
- Updated documentation (README.md, CLAUDE.md, CHANGELOG.md)

## Migration Impact
- Root package.json now manages workspaces
- Build commands delegate to web-app workspace
- All file history preserved via git mv
- Docker build process updated for workspace structure

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

web-app/app/ui/EnterOrSignInButton.tsx

@@ -0,0 +1,38 @@
+import { FC } from 'react';
+
+import { SignInButton } from '@/app/ui/SignInButton';
+import Image from 'next/image';
+import { getTranslations } from "next-intl/server";
+import Link from 'next/link';
+import { paragraphFormatFactory } from '../lib/paragraphFormatFactory';
+import { AuthProvider } from '../lib/getProviders';
+
+export const EnterOrSignInButton: FC<{ session: any, locale: string, providers: AuthProvider[] }> = async ({ session, locale, providers }) => {
+  const paragraphFormat = paragraphFormatFactory(locale);
+
+  const t = await getTranslations("login-page");
+
+  return (
+    <>
+      <span className="flex justify-center mt-4">
+        {
+          session ? (
+            <Link
+              href={`/${locale}/home`}
+              className="btn btn-neutral btn-lg"
+            >
+              <Image src="/icon2.png" alt="logo" width={32} height={32} />
+              {t("main-card.go-to-app")}
+            </Link>
+          ) : (
+            Object.values(providers).map((provider) => (
+              <div key={provider.name}>
+                <SignInButton provider={provider} />
+              </div>
+            ))
+          )
+        }
+      </span>
+      {t.rich("disclaimer", paragraphFormat)}
+    </>);
+};