fix(Fenrir): added 'systemwindow' container for older chapters

[D3ICIDE]

some of the older chapters use "systemWindow" container instead of "doc", not sure if "systemWindow" has completely replaced "doc" so kept both. "systemWinow" has same structure as doc so a very minimal change is required.
Also changed the sorting parameter from "order-by" to "sort"(this is unrelated but thought it was a small enough change to not warrant its own pr)

Closes: #2605

Checklist

• Update version code if an existing plugin was modified
• Test changes in Plugin Playground or the app
• Reference related issues in the PR body (e.g. Closes #xyz)
• Commit messages follow type(scope): description (e.g. feat(<generator>): add new source)

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[greptile-apps]

Confidence Score: 5/5

[Medium risk] Adds support for a new content container type in a manga plugin.

The PR appears safe to merge; no actionable issue was established.

Summary

The PR bumps the Fenrir Realm plugin version and parses systemWindow chapters using the existing doc conversion path.

_{Reviews (1) · Last reviewed commit: "added system 'systemWindow' to parsedCon..."}

[D3ICIDE]

@rajarsheechatterjee works in local app and playground