Feature Request: Add Web Authentication support (same as AltMount)

[Haldir31]

Description
It would be very useful if Postie could support the same Web Authentication mechanism that already exists in AltMount.

Rationale

AltMount already implements web authentication to protect its UI and API.

Postie currently has no built-in authentication, which makes it harder to expose securely.

Reusing or adapting the existing implementation from AltMount would provide consistency across both projects.

Requested change

Add the same authentication support from AltMount into Postie (no new features needed, just reuse/adapt the existing code).

Benefit

Unified and secure access control across AltMount and Postie.

Easier deployment in environments where both tools are used together.

[javi11]

I will add it in the future but you can use an authelia or something in front of it for the moment. This is more complicated than altmount because is also a desktop app