[6.x] Fix TypeError with CarbonImmutable in Timezone Support

[ajnsn]

The improved timezone handling introduced in PR #11409 causes a TypeError when CarbonImmutable instances are used:

Statamic\Http\Middleware\Localize::Statamic\Http\Middleware{closure}(): Argument #1 ($date) must be of type Carbon\Carbon, Carbon\CarbonImmutable given

The callback in the Localize middleware type-hints the parameter as Carbon\Carbon, but Laravel's Date facade can return both Carbon and CarbonImmutable instances depending on the application configuration. This also affects applications using custom DTOs that utilize CarbonInterface.

This PR replaces the Carbon\Carbon type hint with Carbon\CarbonInterface in both affected middleware classes. Since both Carbon and CarbonImmutable implement CarbonInterface.

Example

In our application, we have a custom EventData DTO that uses CarbonImmutable for all date properties:

    readonly class EventData
    {
        public function __construct(
            public CarbonImmutable $starts_at,
            public CarbonImmutable $ends_at,
            // ...
        ) {}
    }

We combine these external event DTOs with Statamic entries in our Events component, merging them into a unified collection.