feat: add Ionos DNS Provider

[andrexlenx]

What this PR does / why we need it?

What this PR does:

• Adds Ionos and Ionos Cloud to the list of supported DNS providers for automated SSL certificate generation (DNS-01 challenge).
• Updates the frontend UI (index.vue) to include specific form fields for these providers:
  • Ionos: Requires API Prefix and API Secret.
  • Ionos Cloud: Requires API Token.

Why we need it:

Currently, users who manage their domains through Ionos or Ionos Cloud cannot automate their SSL certificate provisioning through the platform.

Summary of your change

Backend: New DNS Provider Support

• Added imports and configuration logic for ionos and ionoscloud providers in agent/utils/ssl/dns_provider.go, including new handling for their credentials and API parameters. [1] [2]
• Updated the DnsType enum to include Ionos and IonosCloud.
• Added a new APIPrefix field to the DNSParam struct to support Ionos API credential requirements.
• Reordered the enum for clarity.

Frontend: UI and Validation Updates

• Added Ionos and Ionos Cloud to the selectable DNS types in the frontend (frontend/src/global/mimetype.ts).
• Updated the DNS account creation form to support input fields for Ionos (apiPrefix, apiSecret) and Ionos Cloud (token), including validation rules for these new fields. [1] [2]

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.
  • In case of a merge, Ionos and Ionos Cloud should be added to the supported DNS providers list here: https://1panel-dev.github.io/docs/v2/user_manual/websites/certificate_dns/