Revert "feat(extension): 多模态视频理解开关 + 抽帧/拼图参数（对齐 web NoteForm）"

[JefferyHcool]

Reverts #353

[Copilot]

Pull request overview

This PR reverts the extension-side support for “视频理解（多模态）” that was previously added to align the extension UI/request payload with the web NoteForm (reverting PR #353).

Changes:

• Removes the “视频理解（多模态）” UI controls (toggle + interval/grid inputs) from the popup and options page.
• Stops sending video_understanding, video_interval, and grid_size in extension /generate_note requests.
• Removes the related settings/request fields from the extension’s TypeScript types and default settings.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
BillNote_extension/src/popup/Popup.vue	Removes popup advanced UI and no longer includes video-understanding fields in the generate request payload.
BillNote_extension/src/options/pages/General.vue	Removes the “视频理解（多模态）” section from the options UI.
BillNote_extension/src/logic/types.ts	Removes video_understanding / video_interval / grid_size from GenerateRequest and Settings types.
BillNote_extension/src/logic/constants.ts	Removes the corresponding defaults from DEFAULT_SETTINGS.
BillNote_extension/src/background/main.ts	Stops including video-understanding fields when starting tasks from the background worker.

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