[Feature] Better filtering options for high frequency feeds (mark article as hidden)

Is your feature request related to a problem? Please describe.

Many RSS feeds may be multi-purpose and contain additional content an end user isn't interested in. While there is the "Mark an article as read" feature, auto-marking as read only hides the article from mobile clients and in the web UI when you explicitly uncheck show read articles. This can result in a very cluttered feed with long gaps between the content the end user is actually interested in.

Use case

Two important feeds I need to keep track of are Red Hat Security Advisories and Microsoft Upgrade Guide Vulnerabilities. These are both custom feeds that pull from Red Hat's and Microsoft's respective JSON APIs. For these feeds, I'm only interested in the specific products I manage, not everything else that these firehoses inform me of.

Using article tags and intitle:, I can filter for the things I'm interested in, however due to how quickly these feeds move it's impractical for me to have them in the main stream. Reviewing these streams is also a chore since I can't easily see where to pick up from, as I have hundreds of auto-read articles between the few articles I have manually marked read or have yet to be read.

only articles that would not be auto-read by my existing filters are marked as unread; 128 auto-read articles above CVE-2026-47294 not shown

This is also a problem, albeit less so, with many YouTube channels. YouTube provides no way to filter out shorts or livestreams with query options, so a FreshRSS user uninterested in this content would have to use auto-mark-as-read to ignore these uploads. Since many channels upload multiple shorts at once, or may go live frequently, this clutters the feed of what the end user is actually interested in.

only articles that would not be auto-read by my existing filters are marked as unread

Describe the solution you’d like

An additional per-feed "Mark an article as hidden…" filtering option to mark articles as to not show by default would fix this issue. This could be exposed in the web UI as button to show/hide hidden articles as currently exists for read/unread and favorited/not favorited.

This issue primarily effects the web UI, as mobile clients using the GReader API do not receive marked-as-read articles. While this could be done client-side, for the more egregious examples like MUGV, I would be somewhat concerned as to the performance impact that could have on low-end machines.

Describe alternatives you’ve considered

While an end user can uncheck show read in the web UI, this hides both auto-read articles and manually read articles. An end user could work around this by favoriting a manually read article before moving on, however then favorited articles in that feed lose their meaning to the end user beyond "I read this".

Additional context

While web scraping is mentioned here, this issue effects all feed types in general, including RSS and Atom feeds.