Missing Health Check Endpoints in All Microservices - Team 065

## Description
The architecture diagram in README.md documents `/health` endpoints for all three microservices (order_service, product_service, user_service), but these endpoints are not implemented in the actual code.

## Current Behavior
- Calling `GET /health` on any service returns 404 Not Found
- No health check endpoints exist in app.py files

## Expected Behavior
Each service should respond to `GET /health` with:
- Status code: 200 OK
- JSON response indicating service health and database connectivity

## Location
- `user_service/app.py`
- `product_service/app.py`
- `order_service/app.py`

## Impact
- Cannot use health checks for container orchestration
- Documentation-code inconsistency
- Missing critical production feature

## Suggested Solution
Implement `/health` endpoint in each service that:
1. Returns 200 OK if service is healthy
2. Checks database connectivity
3. Returns appropriate JSON response

Start by comparing README.md with the three entry points: user_service/app.py, product_service/app.py, and order_service/app.py. Exercise GET /health on each service and define done as every endpoint returning 200 with JSON that reports service health and database connectivity.

Written by the indexing model from the issue text.