feat(settings): one look for every user and admin settings page

The settings pages had grown into a mix of styles: folds, dialogs behind
rows, full-width rows next to boxed ones, pills for every figure and buttons
in four sizes. Every page now uses the same kit.

- Cards keep their tinted head band; every part of a card is a rounded block
  with its own small head (SettingsBlock), and rows sit in rounded boxes.
- Nothing folds and nothing hides behind a dialog: the MCP config, OAuth
  scopes, mail how-to, AI privacy note and addon sub-options are all shown.
- Each page is split into two columns balanced by length (SettingsColumns).
- Long explanations moved into an info mark next to the label (HintMark).
- One button size everywhere (text-control); tab names are one word.
- Admin: the old Settings tab is split into Security and Services
  (?tab=settings still opens Security, and the phone keeps its single
  Settings section for both); the Integration group is gone, live flights
  and mail import sit next to the addons they configure.
- Addons: one card per type with rows, no search, filter or fold.
- Quota, TREK API facts, mail import status and Google's daily limit are
  compact lines and strips instead of tiles and pills.
- Language is a select; routing has its own card under the defaults;
  storage saves from the foot of its categories card.
- Unused keys, FoldSummary and the page-width wrapper are removed.

client/src/components/Settings/Section.tsx

@@ -9,22 +9,24 @@ interface SectionProps {
    * standing in for a glyph gets sized by the same utilities.
    */
   icon: LucideIcon | React.ComponentType<{ className?: string }>
+  /** The icon is a brand badge that fills its tile instead of a glyph in it. */
+  iconFill?: boolean
   badge?: React.ReactNode
   /** One line under the title in the head band. */
   hint?: React.ReactNode
   /** A control on the right of the head band. */
   action?: React.ReactNode
-  /** Where a link lands and, for a collapsible card, what it is remembered by. */
+  /** Where a link lands: `#id` scrolls to the card, or opens it from an overview. */
   id?: string
-  /** Shut until its head is clicked, the badge saying its state meanwhile (see settingsKit). */
-  collapsible?: boolean
   children: React.ReactNode
 }
 
-/** A settings group: the planner's card with a head band (see settingsKit). */
-export default function Section({ title, icon, badge, hint, action, id, collapsible, children }: SectionProps): React.ReactElement {
+/**
+ * A settings group: the planner's card with a head band (see settingsKit).
+ */
+export default function Section({ title, icon, iconFill, badge, hint, action, id, children }: SectionProps): React.ReactElement {
   return (
-    <SettingsCard icon={icon} title={title} badge={badge} hint={hint} action={action} id={id} collapsible={collapsible}>
+    <SettingsCard icon={icon} iconFill={iconFill} title={title} badge={badge} hint={hint} action={action} id={id}>
       {children}
     </SettingsCard>
   )