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/Settings.tsx

@@ -466,6 +466,7 @@ function MachineEditor({
 						</Alert>
 						<div className="flex flex-row flex-wrap items-center gap-2">
 							<Button
+								className="mobile-touch-target"
 								variant="outline"
 								onClick={onValidateSSH}
 								disabled={
@@ -678,6 +679,7 @@ function SSHKeyManager({
 					</div>
 					<div className="flex flex-row flex-wrap items-center gap-2">
 						<Button
+							className="mobile-touch-target"
 							disabled={saveKey.isPending}
 							onClick={async () => {
 								await saveKey.mutateAsync(draft);
@@ -687,6 +689,7 @@ function SSHKeyManager({
 							{editing ? "Update key" : "Save key"}
 						</Button>
 						<Button
+							className="mobile-touch-target"
 							variant="outline"
 							disabled={generateKey.isPending}
 							onClick={async () => {
@@ -710,11 +713,16 @@ function SSHKeyManager({
 						>
 							{generateKey.isPending ? "Generating..." : "Generate key"}
 						</Button>
-						<Button variant="outline" onClick={clear}>
+						<Button
+							variant="outline"
+							onClick={clear}
+							className="mobile-touch-target"
+						>
 							Clear
 						</Button>
 						{selectedKey && (
 							<Button
+								className="mobile-touch-target"
 								variant="destructive"
 								onClick={() => deleteKey.mutate(selectedKey.id)}
 							>
@@ -780,7 +788,11 @@ function ResetLocalDatabaseCard() {
 						Reset the local SQLite settings/media index databases after
 						acknowledging the data loss.
 					</p>
-					<Button variant="destructive" onClick={() => setOpen(true)}>
+					<Button
+						variant="destructive"
+						onClick={() => setOpen(true)}
+						className="mobile-touch-target"
+					>
 						Reset local database
 					</Button>
 					{resetDatabase.error && (
@@ -1117,6 +1129,7 @@ export function Settings() {
 											</div>
 											<div className="flex flex-row flex-wrap items-center gap-2">
 												<Button
+													className="mobile-touch-target"
 													variant="outline"
 													onClick={() =>
 														openEditMachine(
@@ -1144,6 +1157,7 @@ export function Settings() {
 													Edit
 												</Button>
 												<Button
+													className="mobile-touch-target"
 													variant="destructive"
 													onClick={() => setDeleteMachineId(selectedMachine.id)}
 												>
@@ -1207,6 +1221,7 @@ export function Settings() {
 					/>
 					{machineDraft.id ? (
 						<Button
+							className="mobile-touch-target"
 							variant="destructive"
 							onClick={() => setDeleteMachineId(machineDraft.id as string)}
 						>
@@ -1266,6 +1281,7 @@ export function Settings() {
 							secondaryAction={
 								machineDraft.id ? (
 									<Button
+										className="mobile-touch-target"
 										variant="destructive"
 										onClick={() => {
 											setDeleteMachineId(machineDraft.id as string);