Docs: Safari can't resolve *.dev.localhost — README access URLs fail

[raix]

Feature description

Problem
The README instructs developers to open the app at https://app.dev.localhost:9000 after starting Aspire. This works in Chrome, Edge, and Firefox but fails in Safari with "Safari cannot find the server app.dev.localhost".

Desired behavior
What should happen when this feature is implemented?

Constraints or considerations
Chrome/Edge/Firefox implement the RFC 6761 convention that resolves localhost and any *.localhost subdomain to the loopback address. Safari (and
the macOS system resolver it relies on for these lookups) only special-cases the bare localhost, not arbitrary subdomains — so
app.dev.localhost and back-office.dev.localhost don't resolve. This is long-standing Safari behavior, not a project bug.

Suggested fix (docs only)

Add a note near the access-URL instructions, e.g.:

Safari users: Safari does not resolve *.localhost subdomains. Either use Chrome/Edge/Firefox, or add the dev hostnames to /etc/hosts:
127.0.0.1 app.dev.localhost
127.0.0.1 back-office.dev.localhost
(/etc/hosts doesn't support wildcards, so each host must be listed; flush DNS afterward with sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder.)

The two hostnames come from application/AppHost/appsettings.json (Hostnames:App and Hostnames:BackOffice).

Environment

• macOS, Safari
• Affects the documented quick-start flow

Feature Type

Documentation

Code of Conduct

• I agree to follow this project's Code of Conduct

[linear]

PP-1315