feat: enable IPv6 on 1panel-network by default

[jakub961241]

Summary

Closes #12202 - Enable IPv6 dual-stack on 1panel-network by default.

Before

EnableIPv6: new(bool)  // pointer to false - IPv6 explicitly disabled

After

EnableIPv6: &enableIPv6  // true
IPAM: {
    Config: [
        {Subnet: "172.18.0.0/16", Gateway: "172.18.0.1"},       // IPv4
        {Subnet: "fd00:1panel::/64", Gateway: "fd00:1panel::1"}, // IPv6 ULA
    ]
}

Uses ULA (Unique Local Address) range fd00:1panel::/64 - no public IPv6 required, works for internal container networking.

Note: Only affects new installations or networks created after this change. Existing users need to recreate the network manually.

Changed file

• agent/utils/docker/docker.go (+8, -1)

feat: Enable IPv6 dual-stack support on 1panel-network by default (#12202)

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[HynoR]

have you checked or compiled your code branch in the test environment?

[jakub961241]

@HynoR Fair question. This change has not been tested in a running 1Panel environment — I don't have a test instance set up at the moment.

The change itself is minimal and straightforward:

• EnableIPv6: new(bool) (pointer to false) → EnableIPv6: &enableIPv6 (pointer to true)
• Added IPAM config with dual-stack subnets

The Docker SDK types are well-documented and this follows the standard pattern for creating dual-stack bridge networks. However, I'd appreciate if a maintainer or community member could verify it on a test instance before merging.

One potential concern: the hardcoded 172.18.0.0/16 subnet could conflict if the user already has a Docker network on that range. The previous code let Docker auto-assign the subnet. If maintainers prefer, I can remove the explicit IPv4 IPAM config and only add the IPv6 subnet.