Fix incorrect channel mapping in My Subscriptions

[FLeXO21]

Fixes #67

My Subscriptions could show the wrong channel contents when selecting
a subscription, especially when the subscription list spans multiple
pages.

The subscriptions were fetched in paginated batches and then sorted
locally by title using _renderList(..., 'title'). This can make the
ordering inconsistent between pagination requests, causing the displayed
subscription to no longer correspond to the expected channel.

This change lets the YouTube API perform the sorting instead:

• add order => 'alphabetical' to the subscriptions request
• remove the additional local title sorting

Tested on a running Lyrion Media Server installation where the issue
was reproducible before the change.

Before:

• subscriptions were visible
• selecting some channels opened content belonging to another subscription
• entries appeared shifted or seemingly random

After:

• subscription order is stable
• selecting a subscription consistently opens the correct channel