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/NoteBox.tsx

@@ -0,0 +1,8 @@
+import { CogIcon } from "@heroicons/react/24/outline";
+import { FC, ReactNode } from "react";
+
+export const NoteBox: FC<{ children: ReactNode }> = ({ children }) =>
+
+<div className="group border border-gray-800 rounded-lg p-2 mb-1 max-w-md">
+  <div className="mt-2 italic text-sm"><CogIcon className="w-6 h-6 inline mt-[-.3em] text-blue-400" /> {children}</div>
+</div>