Low image resolution when using "Copy as Image" causes text recognition/OCR errors

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Issue Title
Low image resolution when using "Copy as Image" on macOS (v0.27.3) leads to OCR/text recognition errors

Issue Description
Describe the bug
When using the "Copy as Image" feature in AFFiNE (v0.27.3) on macOS, the exported image resolution is too low. The text in the copied image becomes blurry and pixelated, causing frequent recognition errors when processed by OCR (Optical Character Recognition) tools.

To Reproduce

Open a page or canvas containing clear text in AFFiNE.

Select the content and perform "Copy as Image" via the context menu.

Paste the image into an OCR application, note-taking app, or preview window.

Observe the blurry text rendering and low DPI, which leads to failed or inaccurate text recognition.

Expected behavior
The exported image should support high-DPI/Retina display scaling (or provide scale options such as 2x / 3x) to ensure text remains sharp and readable for OCR tools.

Environment / Context

AFFiNE Version: 0.27.3

OS: macOS

App Type: Desktop App

Additional context
Increasing the default image export resolution or scale factor on macOS (especially for Retina displays) would resolve this issue.