refactor(access-control): keep chat and files toggles in the platform registry

The first pass pulled hideDeployChatbot out of the declarative platformFeatures
array and hand-rolled a Chat section beside the existing bespoke Files one. That
forfeited search, status filtering, Select All, category grouping and the Info
hint, and the replacement platformSectionVisible re-implemented two of those
with different semantics — searching 'deploy' or 'deployment' hid the very
control named Deployment, and Select All silently skipped both toggles.

Both toggles are now ordinary registry entries under their own Chat and Files
categories, with an id-keyed featureExtras map supplying the nested auth-mode
dropdown. Search, filtering, Select All, hints and the empty state are correct
by construction, and the parallel filter pipeline is gone.

Also from the review:
- index the allow-lists into Sets so per-row membership checks are O(1)
- split the search and status passes so the common 'all' filter returns the
  searched list by reference and a checkbox toggle no longer re-sorts ~180 rows
- extract StatusFilterChip and AuthModeField instead of stamping out the
  dropdowns three and two times
- derive nameChanged/descriptionChanged once instead of repeating the
  comparisons in the save payload
- lock the config key-order invariant the dirty check depends on with a test

Author: waleedlatif1