[1.x] feat: add setting to disable sticky pinning on All Discussions page

[gianniguida]

Summary

Adds an admin setting flarum-sticky.pin_sticky_on_all_discussions (default: true) that controls whether stickied discussions get pinned to the top of the All Discussions page. Tag pages are unaffected.

Motivation

Today, on /all, unread sticky discussions are floated to the top via a UNION query. For communities with long-lived sticky announcements (rules, FAQs, sticky welcome threads), this can push fresh activity down and make /all feel stale — once a user has read the sticky, it returns to its natural position, but a forum with many users will always have some user with an unread sticky, so the pinning is effectively permanent for new visitors.

This adds an opt-out so admins can decide that /all is purely "latest activity," while still relying on sticky pinning inside individual tag pages where it remains useful.

Behavior matrix

Page	Setting true (default)	Setting false
/all	Unread sticky pinned to top (existing behavior)	Sticky at natural last_posted_at position
Tag page	All sticky pinned to top	All sticky pinned to top (unchanged)
Other filters	No pinning	No pinning

Changes

• extend.php — register the setting with a default of true.
• src/PinStickiedDiscussionsToTop.php — inject SettingsRepositoryInterface; before the UNION block, return early when the setting is false.
• locale/en.yml — add admin.settings.pin_sticky_on_all_discussions_{label,help}.
• js/src/admin/index.js — add a boolean toggle in the extension's admin settings tab.

Backwards compatibility

The default value matches existing behavior, so this is a no-op on upgrade. No migration is needed.

Testing

• Admin toggle appears in the extension settings tab and persists across reloads.
• With setting true: /all shows unread sticky at the top, read sticky at natural position (existing behavior).
• With setting false: /all shows all sticky at their natural position; no sticky-induced reordering.
• Tag pages pin sticky to the top in both states.
• Sticky badge, row highlight, and first-post excerpt remain visible regardless of the setting.

Related

This setting is also honored by fof/discussion-language's replacement of PinStickiedDiscussionsToTop, so the toggle takes effect on language-filtered /all views as well.