Touch-target pass: 44px min on default-size buttons (WCAG 2.5.5)

Applies .mobile-touch-target to 32 default-size <Button> elements (32px
tall, below the mobile minimum) across 9 files for strict WCAG 2.5.5
compliance: Save, Cancel, Delete, Validate SSH, Run job, Build index,
Update connection, Add service, etc. Plus the shared DialogFooter Cancel
+ Confirm buttons (used by every ConfirmDialog).

The class applies min-height/min-width: 44px only below md
(max-width: 767px); no-op at md+, so desktop sizing is unchanged.

Completes the touch-target audit started in Slice 9 (which covered icon
buttons, size=sm buttons, checkboxes, switches). 122 tests pass; lint/
build green. No new tests (@media queries aren't honored by jsdom).

Refs openspec/changes/mobile-responsive-parity/verify-report.md residual
risk #2.

frontend/src/pages/Dashboard.tsx

@@ -429,10 +429,20 @@ function ShortcutCard({
 					>
 						Open
 					</Button>
-					<Button size="sm" variant="outline" onClick={onEdit} className="mobile-touch-target">
+					<Button
+						size="sm"
+						variant="outline"
+						onClick={onEdit}
+						className="mobile-touch-target"
+					>
 						Edit
 					</Button>
-					<Button size="sm" variant="destructive" onClick={onDelete} className="mobile-touch-target">
+					<Button
+						size="sm"
+						variant="destructive"
+						onClick={onDelete}
+						className="mobile-touch-target"
+					>
 						Delete
 					</Button>
 				</div>
@@ -503,10 +513,18 @@ export function Dashboard() {
 				description="Quick links to websites today, with room for action and user shortcuts later."
 				action={
 					<div className="flex gap-2">
-						<Button variant="outline" onClick={() => setWidgetDialogOpen(true)}>
+						<Button
+							variant="outline"
+							className="mobile-touch-target"
+							onClick={() => setWidgetDialogOpen(true)}
+						>
 							Edit dashboard
 						</Button>
-						<Button variant="outline" onClick={openCreateShortcut}>
+						<Button
+							variant="outline"
+							className="mobile-touch-target"
+							onClick={openCreateShortcut}
+						>
 							Add shortcut
 						</Button>
 					</div>