Implement Instrumentor for Automatic Metrics Collection

We should add an instrumentor to the ichec_monitor module to enable automatic collection of metrics (request count, duration, errors, etc.) for supported Python projects. This will include:

Middleware for FastAPI and Django to instrument all endpoints automatically. A generic decorator for instrumenting arbitrary Python functions. Documentation and usage examples for each integration. This will make it easier to add consistent observability across our services with minimal code changes.