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/Actions.tsx

@@ -266,7 +266,7 @@ function TaskDialog({
 					confirmBusyLabel="Save action"
 					secondaryAction={
 						onDelete ? (
-							<Button variant="destructive" onClick={onDelete}>
+							<Button variant="destructive" onClick={onDelete} className="mobile-touch-target">
 								Delete
 							</Button>
 						) : undefined
@@ -412,13 +412,13 @@ export function Actions() {
 							description="Open the editor popup to modify this action."
 							action={
 								<div className="flex flex-row flex-wrap items-center gap-2">
-									<Button
+									<Button className="mobile-touch-target"
 										variant="outline"
 										onClick={() => openEdit(initialFromTask(editingTask))}
 									>
 										Edit
 									</Button>
-									<Button
+									<Button className="mobile-touch-target"
 										disabled={runTask.isPending || !runServiceId}
 										onClick={async () => {
 											await runTask.mutateAsync({
@@ -515,7 +515,7 @@ export function Actions() {
 								description="Select a saved action from the list on the left to view its details, run it, or open the editor popup. Use the button at the bottom to add a new action."
 							>
 								{tasks[0] && (
-									<Button variant="outline" onClick={() => setTab(tasks[0].id)}>
+									<Button variant="outline" onClick={() => setTab(tasks[0].id)} className="mobile-touch-target">
 										Select first action
 									</Button>
 								)}