Thunderbird 140 ESR

[HorlogeSkynet]

Description

• Upstream mailnews.js comparison (https://searchfox.org/comm-esr128/source/mailnews/mailnews.js & https://searchfox.org/comm-central/source/mailnews/mailnews.js)
• Arkenfox v128.0 -> v140.0 migration (arkenfox/user.js@128.0...140.0)
• mailnews.headers.showUserAgent (9121) enforcement

How has this been tested ?

140.3.0 on Debian 12.

Types of changes :

• Bug fix (non-breaking change which fixes an issue)
• Typo / style fix (non-breaking change which improves readability)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist :

• My changes looks good ;
• I agree that my code may be modified in the future ;
• My code follows the code style of this project (see .eslint.config.mjs).

[Dupond]

Sorry, I don't use Thunderbird anymore; I find it too slow and too complex for the simple use (just sending emails) that I have. So I've been using Claws Mail for a few months now...