Muesli: PR 11.1 - Performance policy

[fosterfarrell9]

This PR provides the backend foundation for student performance policies for campaigns.

[Copilot]

Pull request overview

Adds backend support for a new student_performance registration policy kind, including validation, evaluation, and UI wiring, to serve as the foundation for campaign performance gating.

Changes:

• Introduces Registration::Policy::StudentPerformanceHandler and wires it into Registration::Policy#handler.
• Extends policy form handling/strong params to support selecting a lecture for the policy.
• Adds specs and i18n strings for validating and evaluating the new policy behavior.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
spec/models/registration/policy_spec.rb	Adds model validation specs for student_performance config/lecture existence.
spec/models/registration/policy_engine_spec.rb	Adds eligibility evaluation coverage for student_performance policies across phases.
spec/models/registration/policy/student_performance_handler_spec.rb	New unit specs for handler evaluate/validate/summary behavior.
spec/factories/registration_policies.rb	Ensures :student_performance trait auto-populates lecture_id in config.
config/locales/registration/en.yml	Adds validation error strings for lecture selection.
config/locales/registration/de.yml	Adds validation error strings for lecture selection.
app/models/registration/policy/student_performance_handler.rb	Implements evaluation/validation/summary for the new policy kind.
app/models/registration/policy.rb	Adds lecture_id virtual accessor and routes :student_performance to the new handler.
app/frontend/registration/policies/_form.html.erb	Updates the policy form to use lecture_id virtual attribute (collection_select).
app/controllers/registration/policies_controller.rb	Permits lecture_id in strong params.