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/.env

@@ -0,0 +1,23 @@
+MONGODB_URI=mongodb://root:HjktJCPWMBtM1ACrDaw7@localhost:27017
+
+GOOGLE_ID=355397364527-adjrokm6hromcaaar0qfhk050mfr35ou.apps.googleusercontent.com
+GOOGLE_SECRET=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
+AUTH_SECRET=Gh0jQ35oq6DR8HkLR3heA8EaEDtxYN/xkP6blvukZ0w=
+
+LINKEDIN_ID=776qlcsykl1rag
+LINKEDIN_SECRET=ugf61aJ2iyErLK40
+USE_MOCK_AUTH=true
+
+MAX_BILL_ATTACHMENT_UPLOAD_SIZE_KB=1024
+MAX_PROOF_OF_PAYMENT_UPLOAD_SIZE_KB=1024
+
+# Share link security
+SHARE_LINK_SECRET=fb831e43b5ab594106e093f86fa8cb2a2405c564a61c3a7681079ec416528654
+
+# Share link TTL configuration
+SHARE_TTL_INITIAL_DAYS=10
+SHARE_TTL_AFTER_VISIT_HOURS=1
+
+# Rate limiting for uploads
+UPLOAD_RATE_LIMIT_PER_IP=5
+UPLOAD_RATE_LIMIT_WINDOW_MS=3600000