Add comprehensive GitHub Copilot instructions and CodeRabbit configuration for WRKFLW monorepo development

.coderabbit.yml

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+---
+reviews:
+  pre_merge_checks:
+    custom_checks:
+      - name: "Undocumented Breaking Changes"
+        mode: "warning"
+        instructions: |
+          Pass/fail criteria: All breaking changes to public APIs, CLI flags,
+          environment variables, configuration keys, database schemas, or
+          HTTP/GraphQL endpoints must be documented in the "Breaking Change"
+          section of the PR description and in CHANGELOG.md. Exclude purely
+          internal or private changes (e.g., code not exported from package
+          entry points or explicitly marked as internal).

.github/copilot-instructions.md

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+# ConstructionOnline WRKFLW - Copilot Instructions
+
+ALWAYS reference these instructions first and fallback to search or bash commands only when you encounter unexpected information that does not match the info here.
+
+## Overview
+WRKFLW is a construction management monorepo containing a starter implementation for ConstructionOnline MVP. The repository includes a TypeScript Express backend, React frontend, Expo React Native mobile app, and Terraform infrastructure configuration. The current implementation is a multi-timezone clock demo that demonstrates the full stack architecture.
+
+## Working Effectively
+
+### Prerequisites and Environment Setup
+- Node.js v20.19.5 and npm 10.8.2 are available and working
+- The repository uses npm workspaces with 4 sub-projects: backend, frontend, mobile, infra
+- All package installations and builds have been validated to work
+
+### Initial Setup Commands
+Run these commands in order to set up the development environment:
+
+```bash
+# Install root workspace dependencies - takes 6 seconds, NEVER CANCEL
+npm install
+
+# Install missing TypeScript definitions for backend (required)
+cd backend && npm install --save-dev @types/cors @types/luxon
+
+# Install missing TypeScript definitions for frontend (required)  
+cd frontend && npm install --save-dev @types/react @types/react-dom typescript
+```
+
+### Build and Test Commands
+Execute these commands to build and validate the codebase:
+
+```bash
+# Build backend - takes 2 seconds
+cd backend && npm run build
+
+# Build frontend - takes 5 seconds  
+cd frontend && npm run build
+
+# Start backend development server
+cd backend && npm run dev
+# Backend will be available at http://localhost:4000
+
+# Start frontend development server (in new terminal)
+cd frontend && npm start  
+# Frontend will be available at http://localhost:3000
+
+# Start both backend and frontend concurrently from root
+npm start
+```
+
+### Critical Build Information
+- **NEVER CANCEL** any npm install or build commands - they complete quickly (under 10 seconds each)
+- Root dependency installation: 6 seconds
+- Backend build: 2 seconds  
+- Frontend build: 5 seconds
+- Backend startup: instant
+- Frontend startup: 10-15 seconds
+- Mobile app **WILL FAIL** due to network restrictions preventing access to api.expo.dev - this is expected
+
+### Working Applications and Validation
+
+#### Backend API (Express + TypeScript)
+- **Location**: `backend/src/index.ts`  
+- **Port**: 4000
+- **Endpoints**:
+  - GET `/api/health` - Health check
+  - GET `/api/timezones` - List default timezones
+  - POST `/api/time` - Get current time for specified timezones
+- **Validation**: All endpoints tested and working
+- **Example**: `curl http://localhost:4000/api/health` returns `{"status":"ok","now":"..."}`
+
+#### Frontend Web App (React + TypeScript)  
+- **Location**: `frontend/src/App.tsx`
+- **Port**: 3000
+- **Functionality**: Multi-timezone clock with add/remove timezone capability
+- **Validation**: Fully tested - can add timezones (e.g., "Asia/Shanghai"), remove timezones, real-time clock updates
+- **Screenshot**: ![Working Frontend](https://github.com/user-attachments/assets/e514cdd2-4d6d-4207-af32-9a62eb33f5de)
+- **Manual Testing**: Always test timezone addition/removal functionality after making changes
+
+#### Mobile App (Expo React Native)
+- **Location**: `mobile/App.js`
+- **Status**: **CANNOT RUN** - fails with network errors trying to reach api.expo.dev
+- **Expected Error**: `FetchError: request to https://api.expo.dev/v2/versions/latest failed`
+- **Note**: This is expected in sandboxed environments. Do not attempt to fix - document as limitation
+
+#### Infrastructure (Terraform)
+- **Location**: `infra/terraform/main.tf`
+- **Contents**: AWS S3 bucket configuration for asset storage
+- **Note**: Cannot be applied without AWS credentials
+
+## Repository Structure Reference
+
+### Root Directory
+```
+├── package.json          # Workspace configuration, concurrently script
+├── README.md             # Basic setup instructions  
+├── PRD.md               # Comprehensive product requirements (290 lines)
+├── openapi.yaml         # API specification stub
+├── graphql/schema.graphql # GraphQL schema stub
+├── seed-data.json       # Sample data (users, projects, tasks)
+├── backend/             # Express TypeScript API
+├── frontend/            # React TypeScript web app
+├── mobile/              # Expo React Native app (non-functional)
+└── infra/               # Terraform AWS configuration
+```
+
+### Backend Structure
+```
+backend/
+├── package.json         # Express, cors, luxon dependencies
+├── tsconfig.json        # TypeScript configuration
+└── src/index.ts         # Main server file with timezone API
+```
+
+### Frontend Structure  
+```
+frontend/
+├── package.json         # React, react-scripts dependencies
+├── tsconfig.json        # TypeScript configuration (created during setup)
+├── public/index.html    # HTML template
+└── src/
+    ├── index.tsx        # React root
+    └── App.tsx          # Main timezone clock component
+```
+
+## Development Workflow
+
+### Making Changes
+1. **Always start both backend and frontend** before testing changes:
+   ```bash
+   # Terminal 1
+   cd backend && npm run dev
+
+   # Terminal 2  
+   cd frontend && npm start
+   ```
+
+2. **Test API changes**: Use curl to test backend endpoints:
+   ```bash
+   curl http://localhost:4000/api/health
+   curl http://localhost:4000/api/timezones
+   ```
+
+3. **Test frontend changes**: Navigate to http://localhost:3000 and test:
+   - Add a new timezone (e.g., "Europe/Paris")  
+   - Remove an existing timezone
+   - Verify times update every second
+   - Verify proper error handling for invalid timezones
+
+### Production Builds
+```bash
+# Build for production
+cd backend && npm run build && npm start
+cd frontend && npm run build
+```
+
+### Troubleshooting Common Issues
+
+#### Frontend Module Resolution Error
+If you see `Module not found: Error: Can't resolve './App'`:
+- Ensure `frontend/tsconfig.json` exists (it gets created during setup)
+- Verify `@types/react` and `@types/react-dom` are installed
+
+#### Backend Type Errors
+If you see TypeScript errors for `cors` or `luxon`:
+- Install missing types: `npm install --save-dev @types/cors @types/luxon`
+
+#### Port Already in Use
+If backend fails with `EADDRINUSE` on port 4000:
+- Stop existing processes: `pkill -f "npm run dev"`
+- Or use different port: `PORT=4001 npm run dev`
+
+## Key Files for Common Tasks
+
+### API Development
+- Modify `backend/src/index.ts` for new endpoints
+- Update `openapi.yaml` for API documentation
+- Reference `seed-data.json` for data structure examples
+
+### Frontend Development  
+- Modify `frontend/src/App.tsx` for UI changes
+- Component uses React hooks (useState, useEffect)
+- Styling is inline (no CSS files)
+
+### Adding Dependencies
+```bash
+# Backend dependencies
+cd backend && npm install <package>
+
+# Frontend dependencies  
+cd frontend && npm install <package>
+
+# Root dependencies (affects all workspaces)
+npm install <package> -w backend -w frontend
+```
+
+## Validation Requirements
+
+### Always Test These Scenarios
+1. **Backend API**: All 3 endpoints respond correctly
+2. **Frontend Clock**: 
+   - Shows current time for all default timezones
+   - Can add new timezone (try "Asia/Kolkata")
+   - Can remove timezone (click Remove button)
+   - Times update every second
+3. **Error Handling**: Try invalid timezone like "Invalid/Zone"
+
+### Never Skip These Steps
+- Run both `npm run build` commands before committing
+- Start both services and verify they work together
+- Test at least one complete user scenario (add/remove timezone)
+- Verify no console errors in browser developer tools
+
+## Expected Limitations
+- **Mobile app cannot start** due to network restrictions - this is expected
+- **No linting/testing infrastructure** - only build validation available
+- **No CI/CD pipelines** - manual testing required
+- **No database** - all data is in-memory/client-side
+
+This codebase provides a solid foundation for construction management features but currently implements only timezone functionality as a proof of concept.

.gitignore

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+node_modules/
+dist/
+.env
+.env.local
+*.log
+frontend/node_modules/
+backend/node_modules/
+mobile/node_modules/