sort tag suggestions by frequency or recency

# Related issue

Related to #1021, which has a `Sort tags by frequency` unchecked item.

# Problem

I use a tag called `wallabako` to mark articles I want to read on my Kobo. Every time I save a link I have to open the tags screen, and because `wallabako` is alphabetically at the bottom of my list, I have to scroll down to it each time, or use the filter. This is a small annoyance, but I believe it can be improved.

# Ideas

See below a few ideas I thought of that could make it easier to add frequently used tags:

- **Sort by frequency** — tags used most often across all articles float to the top (same as #1021).
- **Sort by recency** — tags applied most recently appear first (useful when processing a batch of articles on the same topic, as noted in a comment in #1021).
- **Pinned / favourite tags** — a small set of explicitly starred tags always shown first, before any filtering.

I don't have a strong personal preference as long at most of the time the tag I'm looking for is directly visible when I open the tags screen.

### Offer to help

I'm a software engineer, and I'm happy to contribute to the design and implementation if the idea is agreed on.

Sincerely,
Manuel