fix: align generation options with current API

[voodoohop]

• Removes retired image and video controls and aligns safety descriptions with the current API.
• Supports current video durations and keeps model selectors dynamic.
• Accepts server Secret Keys and user-authorized BYOP sk_ tokens, validating them through the scope-free /account/key endpoint.
• Updates current endpoint, credential, model-capability, and BYOP documentation.

Validation:

• Jest: 26/26
• n8n-node build
• n8n-node lint
• git diff --check

Existing binary image-to-image upload behavior is unchanged and can be handled separately from this compatibility cleanup.