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/Admin/AddonSubRow.tsx

@@ -33,7 +33,8 @@ export default function AddonSubRow({
   onToggle: () => void
 }) {
   return (
-    <li className="flex min-h-[44px] items-center gap-2.5 px-3 py-1.5">
+    // Indented under the addon's name (16 + 32 + 12 px), one step quieter than it.
+    <li className="flex min-h-[44px] items-center gap-2.5 py-1.5 pe-4 ps-[60px]">
       {icon
         ? <span className={`grid h-6 w-6 flex-none place-items-center ${enabled ? 'text-content-muted' : 'text-content-faint'}`}>{icon}</span>
         : <span className="w-6 flex-none" aria-hidden />}