feat: align framework updates with core templates

[cshiels-ie]

Summary

This PR aligns framework updates with the way platform services are structured.

• Updates the generated framework workflow to run the project and core framework updates together.
• Makes a normal platform-service-framework update update the project plus every apps/* directory with Copier answers, including core and newly added platform systems.
• Retains --core as a backward-compatible flag.
• Adds configurable core service_type support for services such as metrics-service.
• Preserves service-specific app customizations while allowing Copier to report conflicts.
• Keeps feature-flag registration in the framework core template.
• Documents that public health extensions must sanitize exception details.
• Adds regression coverage for service-type propagation and managed-app update dispatch.

A temporary metrics-service trial confirmed that the update is non-trivial but reviewable:

• Project-level conflicts are limited to Dependabot/workflow customizations.
• Core-level conflicts identify the expected custom merge points: resource registry, template tags, and custom health checks.
• The metrics-specific service_type = "metrics", Segment checks, and other service customizations remain available for manual conflict resolution.
• The real metrics-service checkout was not modified.

Testing

• Ruff checks: passed.
• Managed-app update regression test: passed.
• Full tests/test_update.py: 2 passed, 3 environment-dependent failures because the local template checkout is intentionally dirty and the existing tests require a clean template repository.
• Temporary metrics-service Copier update trial completed successfully and produced the expected conflict set.

AI Assistance

This change was developed with assistance from Codex. All generated code was reviewed and tested before submission.