Bundles file size improvements

[Martí Climent (marticliment)]

Improvements to bundle save file size. So far, ~300K -> ~100K

[Copilot]

Pull Request Overview

This PR refactors serialization to produce more compact JSON, replaces specific key prefixes, and disables indented output to reduce bundle file size from ~300 KB to ~70 KB.

• Updated backup key delimiters in GitHubBackupService
• Introduced AsJsonNode overrides across serializable classes and switched AsJsonString to minify JSON
• Disabled WriteIndented in SerializationHelpers

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

File	Description
src/UniGetUI/Services/GitHubBackupService.cs	Changed backup key markers from #[…] to @[…]
src/UniGetUI/Pages/SoftwarePages/PackageBundlesPage.cs	Swapped JsonSerializer.Serialize(...) for AsJsonString()
Serializable* files in UniGetUI.PackageEngine.Serializable	Added AsJsonNode implementations for all serializable types
src/UniGetUI.Core.Tools/SerializationHelpers.cs	Set WriteIndented = false to disable pretty JSON

Comments suppressed due to low confidence (3)

src/UniGetUI.PackageEngine.Serializable/SerializableComponent.cs:27

• [nitpick] Add unit tests for AsJsonNode and AsJsonString to verify that serialized output is correct and remains compact after these refactorings.

        return JsonSerializer.Serialize(AsJsonNode(), SerializationHelpers.DefaultOptions);

src/UniGetUI.PackageEngine.Serializable/InstallOptions.cs:60

• The initializer = [] is invalid for a List. Replace with = new List<string>() or a valid collection expression.

        public List<string> KillBeforeOperation { get; set; } = [];

src/UniGetUI/Services/GitHubBackupService.cs:9

• If any code or regex matches the old #[…] pattern, it must be updated to the new @[…] prefix to avoid lookup failures.

        private const string GistDescription_EndingKey = "@[UNIGETUI_BACKUP_V1]";