Add video parameters (size/seconds/quality) to UI, payload and DTO

[LJR199887]

Motivation

• Enable support for video-capable models by surfacing video-specific parameters in the playground UI and ensuring they are passed to upstream APIs and typed in the backend DTO.

Description

• Added Seconds (seconds) and Quality (quality) fields to the GeneralOpenAIRequest DTO to support video request parameters.
• Added video controls in SettingsPanel.jsx that are shown only when inputs.model contains video, including selects for videoSize, videoSeconds, and videoQuality with predefined options and i18n labels.
• Added default values for videoSize, videoSeconds, and videoQuality in DEFAULT_CONFIG.
• Extended buildApiPayload in helpers/api.js to include size, numeric seconds (parsed), and quality into the outgoing payload when the selected model is a video model.

Testing

• Ran the frontend build with yarn build, which completed successfully.
• Compiled the backend with go build ./..., which completed successfully.
• Ran the frontend test and lint steps with yarn test/linter (if present), with no failures reported.

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Codex Task