feat: Add inline image support in editor

[trabulium]

Summary

Adds support for inline images in the editor, addressing a commonly requested feature.

Changes:

• Paste images directly from clipboard into the editor
• Drag & drop image files into the editor
• Image button in the bubble menu toolbar for file selection
• Upload progress indicator
• Backend fix to serve inline images that are uploaded before the message is sent

Test Plan

• Copy an image to clipboard and paste into editor - should upload and display
• Drag an image file into the editor - should upload and display
• Verify uploaded images display correctly (no 404 errors)

Closes #66

[abhinavxd]

Hi,

This doesn’t seem to work as expected. Inline attachments need to be included directly in the email as MIME parts with a Content-ID for them to render inline.

I tried sending an email the image was not rendering.

Thanks,

[ybizeul]

I can confirm, it doesn't work currently.
I was doing some testing with the most recent version (v0.9.5-beta) and playing around with formatting.

First failure was formatting some code in the email, there doesn't seem to be a style for it, so I did it from my text editor and pasted, or matbe used some triple backquote markdown, not sure what worked, maybe that's relevant for what's next : I then tried to paste a screenshot taken from my mac, and it wouldn't paste anything.
I sent the email anyways, and from a fresh response field I directly pasted, now I could see the image in the editor, but when sending, it was gone, and the email I received was empty as well.

EDIT : I just realized this has not been merged, right ? Delete my comment if not relevant then !