Add integrated server list preview and position selector in Add Server dialog

[SpoilerRules]

Description

Currently, the server add feature only supports Minecraft's default behavior, where newly added servers appear at the end of the list. This limits flexibility for users who prefer more control over where new servers are placed.

To provide a better user experience, the Add Server dialog should include a built-in preview of the server list, allowing users to visually choose where the new server will appear.

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Proposed Solution

Enhance the Add Server dialog with a server list preview panel (placed either beside or below the main form).
This preview allows the user to select where the new server will appear before confirming.

Preview panel features:

• Shows a scrollable preview of the current server list.
• Displays the server being added in a placeholder position within the list.
• Allows users to drag the placeholder to a custom position if desired.
• Includes preset buttons such as:
  • Top
  • Bottom (default, matching Minecraft behavior)
• Selecting a preset instantly moves the server preview to the corresponding position.
• If the user wants a specific placement, they can still scroll or drag to adjust it manually.

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Notes

The design can adapt based on space:

• If the Add Server dialog is wide, the preview can appear on the right side.
• If the dialog is narrow, the preview can appear below the input fields.