Two new sections, both hooked into the precedence-aware features store:
* /settings — "Visible sections" block with one toggle per SectionKey
bound to setUserFeature(). When a collective-level override is
present the toggle is disabled and a one-line "Hidden by the
collective" hint replaces the visible state — making it obvious
why the per-user toggle is moot.
* /collective/manage — "Collective sections" block (admin-only,
inside the existing isAdmin guard) with one toggle per SectionKey
bound to setCollectiveFeature(). Flipping any of them propagates
to every member in realtime via the publication added in the
previous commit.
Both helpers fall back to the default-ON semantics of section_enabled
when the JSONB key is missing, so untouched rows render exactly as
before fase 12.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>