closes #5824

This PR adds dual-stack IPv4/IPv6 support to the repo. Previously, binding the server to standard IP addresses or hostnames restricted connection handling exclusively to a single stack (generally IPv4 only or forced IPv6 only using HOST=::) depending on system defaults. This change allows Open WebUI to listen on both IPv4 and IPv6 interfaces simultaneously when configured.

Changes Proposed

• Configured backend socket/server binding options to enable dual-stack IPv4/IPv6 listening (:: binding with dual-stack socket options enabled).
• Updated backend initialization logic to ensure graceful fallback if dual-stack binding is unsupported by the host environment.
• Verified socket listener behavior across standard IPv4 (127.0.0.1 / 0.0.0.0) and IPv6 (::1 / ::) connections.

Testing Conducted

• Tested locally in a containerized environment listening on dual-stack sockets.
• Verified successful API and WebUI connections over both IPv4 (192.168.x.x / 127.0.0.1) and IPv6 ([::1] / global unicast addresses).
• Confirmed CORS handling and HTTP responses function identically across both stacks.

Checklist

• [x ] This PR targets the dev branch.
• [x ] This PR links to a well-described, confirmed Issue or active Discussion: Closes #5824 / Relates to #___.
• [x ] A maintainer explicitly asked me to open this PR, or this PR only updates i18n/localization.
• [ x] The change is one logical unit with no unrelated commits.
• [x ] I matched nearby code patterns and avoided unnecessary new settings, abstractions, or dependencies.
• [ x] I manually tested the changed workflow and any nearby behavior that could be affected.
• I updated relevant docs, including the Open WebUI Docs Repository, if needed. - not done
• I added screenshots for UI changes, and a recording when motion or interaction matters. - na
• [ x] I reviewed any AI-generated code before submitting it.
• [x ] The PR title uses one of the prefixes listed below.

Contributor License Agreement

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