build(frontend): Bump gix-components to next

[AntonioVentilii]

Motivation

With PR dfinity/gix-components#708, gix-components has migrated Modal to Svelte 5. Since it is quite a breaking change and that component is used throughout the code, we adapt it here in a separate PR using the @next version.

[Copilot]

Pull Request Overview

This PR updates the gix-components library to use the next version that includes the migration of the Modal component to Svelte 5, adapting all Modal usages throughout the codebase to use the new API.

• Updates gix-components to ^8.0.0-next-2025-09-10 in package.json
• Migrates Modal component usage from Svelte 4 event handlers to Svelte 5 props
• Converts slot-based title patterns to Svelte 5 snippet syntax

Reviewed Changes

Copilot reviewed 20 out of 21 changed files in this pull request and generated 1 comment.

File	Description
package.json	Updates gix-components version to next pre-release
Multiple Modal components	Converts on:nnsClose to onClose prop and slot="title" to {#snippet title()}

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