Fix CustomId incorrectly set on link and premium buttons

[Copilot]

Description

CustomId was defined in DiscordComponent base class with a default Guid.NewGuid() value, causing it to be serialized on link buttons (which use URLs) and premium buttons (which use SKU IDs).

Changed CustomId to a virtual property in DiscordComponent without a default value. Override it with Guid.NewGuid() in the 4 component types that require it:

• DiscordButtonComponent
• DiscordBaseSelectComponent
• DiscordTextInputComponent
• DiscordFileUploadComponent

Link and premium buttons now inherit the base property without default initialization, preventing invalid custom_id serialization.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Existing test suite passes without modifications
• Build succeeds across all target frameworks (net8.0, net9.0, net10.0)

Test Configuration:

• SDK: .NET 8.0, 9.0, 10.0

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

@Aiko-IT-Systems/discatsharp

Original prompt

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This section details on the original issue you should resolve

<issue_title>Custom ID is set on component where it shouldn't</issue_title>
<issue_description>We have the CustomId field at https://github.com/Aiko-IT-Systems/DisCatSharp/blob/main/DisCatSharp%2FEntities%2FComponents%2FDiscordComponent.cs#L28-L32

It should be in the DiscordButtonComponent class tho. Right now it would also set custom id for link and premium buttons, but they can't have a custom ID. This field needs to be completely moved. Additionally it needs to be copied over to DiscordBaseSelectComponent. </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Custom ID is set on component where it shouldn't #741

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