New admin-only Users page (sidebar): Users & roles (list + promote/demote with
confirm; self/demo/last-admin guarded server-side), plus the Access requests
(Invite whitelist) and Demo whitelist+reset migrated out of Settings → Account
(same data/tables — UI relocated only). Settings → Account now holds personal
content only. ConfigPanel learns a boolean field type (toggle) for the new
allow_registration setting. api methods, new 'users' page/route/nav/header, and
EN/HU/DE strings (new users namespace + access group).
Register youtube_api_key in the sysconfig registry as a secret and resolve it from
the DB-override-or-env layer in YouTubeClient (self.db is in scope). Adds a YouTube
API group to the Configuration page (EN/HU/DE).
Google OAuth client id/secret stay env-only for now: the authlib client is
registered at module load (auth.py), and the token-refresh reads them too, so a
runtime DB override needs a lazy/re-registerable OAuth client — that belongs to the
install-wizard epic (first-boot OAuth config without restart). Admin-role-via-UI
moves to the auth-overhaul epic (user management lives there).
Add the four new groups to the page's group order and EN/HU/DE labels + field
hints for the 8 newly DB-overridable settings. The page is registry-driven, so
this is purely presentational (group order + i18n).
Per-field Save buttons were an unconventional, endpoint-driven choice. Replace
them with a single drafted Save/Discard bar (consistent with the Settings page):
edits are buffered and applied together on Save (each via the existing per-key
PATCH/DELETE), Discard reverts. Reset-to-default is a per-field affordance applied
on Save too — clearing a non-secret falls back to default; a secret (which can't
be cleared by emptying) gets a toggle that resets it on save. Backend unchanged.
New admin-only Configuration page that renders the system_config registry grouped
(Email/SMTP first), with per-field save/reset, write-only encrypted secret fields
(disabled with a hint when TOKEN_ENCRYPTION_KEY is unset), and a Send-test-email
button. New 'config' page + sidebar nav item + header title; api methods and
EN/HU/DE strings.
