feat: add newsletter feature with subscribers, managers, and EU-compliant unsubscribe

[Copilot]

• Analyse current route names for best-practice issues
• Update routes.ts with consistent dot-notation names:
  • newsletters → management.newsletters
  • newsletter → management.newsletter
  • dashboard → management.camp
  • participants → management.camp.participants
  • room-planner → management.camp.room-planner
  • management.settings → management.camp.settings
  • access → management.camp.settings.access
  • edit-camp → management.camp.settings.edit
  • edit-email-templates → management.camp.settings.emails
  • edit-files → management.camp.settings.files
  • edit-form → management.camp.settings.form
  • newsletter-unsubscribe → newsletter.unsubscribe
• Update all usages in layouts, components, pages, and stores

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[marvin-wtt]

@copilot Make sure that you include all translation locales (en, de, fr, pl, cs). Avoid hard coding translated text (e,g, in the newsletter reason)

[Copilot]

@marvin-wtt The model claude-sonnet-4.6 is not available for your account. This can happen if the model was disabled by your organization's policy or if your Copilot plan doesn't include access to it.

You can try again without specifying a model (just @copilot) to use the default, or choose a different model from the model picker.

If you want to contact GitHub about this error, please mention the following identifier so they can better serve you: 9806d9d5-712a-4a7f-8be7-5ce31f53193b

[Copilot]

@marvin-wtt The model claude-sonnet-4.6 is not available for your account. This can happen if the model was disabled by your organization's policy or if your Copilot plan doesn't include access to it.

You can try again without specifying a model (just @copilot) to use the default, or choose a different model from the model picker.

If you want to contact GitHub about this error, please mention the following identifier so they can better serve you: 9806d9d5-712a-4a7f-8be7-5ce31f53193b

[Copilot]

@marvin-wtt The model claude-sonnet-4.6 is not available for your account. This can happen if the model was disabled by your organization's policy or if your Copilot plan doesn't include access to it.

You can try again without specifying a model (just @copilot) to use the default, or choose a different model from the model picker.

If you want to contact GitHub about this error, please mention the following identifier so they can better serve you: 9806d9d5-712a-4a7f-8be7-5ce31f53193b

[Copilot]

@marvin-wtt The model claude-sonnet-4.6 is not available for your account. This can happen if the model was disabled by your organization's policy or if your Copilot plan doesn't include access to it.

You can try again without specifying a model (just @copilot) to use the default, or choose a different model from the model picker.

If you want to contact GitHub about this error, please mention the following identifier so they can better serve you: 9806d9d5-712a-4a7f-8be7-5ce31f53193b

[Copilot]

@marvin-wtt The model claude-sonnet-4.6 is not available for your account. This can happen if the model was disabled by your organization's policy or if your Copilot plan doesn't include access to it.

You can try again without specifying a model (just @copilot) to use the default, or choose a different model from the model picker.

If you want to contact GitHub about this error, please mention the following identifier so they can better serve you: 9806d9d5-712a-4a7f-8be7-5ce31f53193b

[Copilot]

@marvin-wtt The model claude-sonnet-4.6 is not available for your account. This can happen if the model was disabled by your organization's policy or if your Copilot plan doesn't include access to it.

You can try again without specifying a model (just @copilot) to use the default, or choose a different model from the model picker.

If you want to contact GitHub about this error, please mention the following identifier so they can better serve you: 9806d9d5-712a-4a7f-8be7-5ce31f53193b