[WIP] Pin attachment list to bottom of Email View

[dab246]

Issue

With the current design, the attachment list is pushed to the bottom of the email content. For long emails, users have to spend time scrolling all the way down before they can see the attachments.

Solution

• We will pin the attachments at the bottom of the Email View so that users can always see them.
• Users will be able to expand/collapse this pinned attachment section to view all attachments or hide them.
• The pinned attachment thread will only be displayed for emails that are expanded.
• The maximum height of the pinned widget when expanded is 150dp.
• Add an option in Settings to enable or disable pinned attachments.

Resolved

• Web:

Screen.Recording.2025-09-16.at.3.35.51.PM.online-video-cutter.com.mp4

• Mobile:

Screen_recording_20250916_153912.webm

• Setup in Setting

Screen.Recording.2025-09-17.at.3.15.43.PM.mov

• E2E console:

🧪 Should see save dialog when download all attachments successfully
        ✅   1. waitUntilVisible widgets with type "TwakeWelcomeView".
        ✅   2. tap widgets with text "Use company server".
        ✅   3. waitUntilVisible widgets with type "LoginView".
        ✅   4. tap widgets with type "TextField" descending from widgets with key [<'dns_lookup_input_form'>].
        ✅   5. enterText widgets with type "TextField" descending from widgets with key [<'dns_lookup_input_form'>].
        ✅   6. waitUntilVisible widgets with text "bob".
        ✅   7. tap widgets with text "Next".
        ✅   8. waitUntilVisible widgets with key [<'base_url_form'>] descending from widgets with type "LoginView".
✅ Should see save dialog when download all attachments successfully 

Test summary:
📝 Total: 1
✅ Successful: 1
❌ Failed: 0
⏩ Skipped: 0
📊 Report: ../tmail-flutter/build/app/reports/androidTests/connected/index.html
⏱️  Duration: 50s

🧪 Should auto preview attachment when export attachment successfully
        ✅   1. waitUntilVisible widgets with type "TwakeWelcomeView".
        ✅   2. tap widgets with text "Use company server".
        ✅   3. waitUntilVisible widgets with type "LoginView".
        ✅   4. tap widgets with type "TextField" descending from widgets with key [<'dns_lookup_input_form'>].
        ✅   5. enterText widgets with type "TextField" descending from widgets with key [<'dns_lookup_input_form'>].
        ✅   6. waitUntilVisible widgets with text "bob".
        ✅   7. tap widgets with text "Next".
        ✅   8. waitUntilVisible widgets with key [<'base_url_form'>] descending from widgets with type "LoginView".
        ✅   9. enterText widgets with type "TextField" descending from widgets with key [<'base_url_form'>].
✅ Should auto preview attachment when export attachment successfully 

Test summary:
📝 Total: 1
✅ Successful: 1
❌ Failed: 0
⏩ Skipped: 0
📊 Report: ../tmail-flutter/build/app/reports/androidTests/connected/index.html
⏱️  Duration: 41s

[chibenwa]

Thanks for putting this together @dab246 !

@poupotte @Bobpodvalnyi opinions?

[github-actions]

This PR has been deployed to https://linagora.github.io/tmail-flutter/4020.

[chibenwa]

@dab246 can you post also a screenshot with thread enabled in web/mobile for this?

[dab246]

@dab246 can you post also a screenshot with thread enabled in web/mobile for this?

Please see demo video in description above. Web: 0:05s, Mobile: 0:52s.