Touch-target audit: 44px minimum on mobile interactive elements (Slice 9)

Apply the mobile-touch-target CSS class to 40 interactive elements across
12 files. The class applies min-height/min-width:44px only below md
(max-width:767px), satisfying WCAG 2.5.5 / Apple HIG on touch devices.
Desktop behavior is unchanged.

Audit log (before -> after hit-area):
- App.tsx: hamburger/dark-mode/sign-out (32/32/28 -> 44)
- Dashboard.tsx: shortcut open/edit/delete (28 -> 44), enabled switch (18 -> 44)
- Media.tsx: mobile pagination prev/next (28 -> 44)
- FileBrowser.impl.tsx: 'Open Settings' alert button (28 -> 44)
- UsersPage.impl.tsx: compose toolbar bold/italic/link/list (32 -> 44),
  attachment remove button (16 -> 44)
- Settings.tsx: machine switch (18 -> 44), clear/add-machine buttons (28 -> 44),
  reset-db checkboxes x3 (16 -> 44)
- Actions.tsx: 'Add action' button (28 -> 44)
- ServicePage.tsx: service enabled switch (18 -> 44)
- ServicesPage.tsx: service switch/open-link/delete-icon (18/28/32 -> 44)
- ObservabilityPage.tsx: retry + 4 asChild link buttons (28 -> 44)
- WidgetConfigDialog.tsx: 4 icon buttons (32 -> 44), 2 switches (18 -> 44),
  2 add-widget buttons (28 -> 44)
- SessionActivityPanel.tsx: 'Open in Users' button (28 -> 44)

Deliberately skipped: default-size text buttons (32px, borderline), desktop-only
sidebar toggle, DataTable internals (desktop-only below md), Select triggers.
Dashboard anchor pills and HoverEditButton already had the class from Slices 1/2.

No new tests (the class applies via @media which jsdom doesn't honor).
116 tests pass; lint/build green.

Refs openspec/changes/mobile-responsive-parity/ (spec R6, tasks slice 9).

frontend/src/pages/ServicesPage.tsx

@@ -234,6 +234,7 @@ function CreateServiceDialog({
 							<div className="flex items-center gap-2">
 								<Switch
 									id="service-enabled"
+									className="mobile-touch-target"
 									checked={draft.enabled}
 									onCheckedChange={(checked) =>
 										setDraft({ ...draft, enabled: checked })
@@ -328,6 +329,7 @@ export function ServicesPage() {
 												<Button
 													variant="ghost"
 													size="sm"
+													className="mobile-touch-target"
 													onClick={() =>
 														navigate(`/services/${s.service_type}/${s.id}`)
 													}
@@ -337,7 +339,7 @@ export function ServicesPage() {
 												<Button
 													variant="ghost"
 													size="icon"
-													className="h-8 w-8 text-destructive"
+													className="mobile-touch-target h-8 w-8 text-destructive"
 													onClick={() => setDeleteId(s.id)}
 												>
 													<Trash2 className="h-4 w-4" />