feat(setup): add CLI setup command group for end-to-end speaker provisioning

Add `soundtouch-cli setup` subcommand group covering the full reset →
re-provision → pair lifecycle as a scriptable alternative to the web UI:

  inspect, verify, plan, factory-reset, wait-ap, wifi-push, wait-online,
  ssh-check, install-ca, migrate, reboot, pair (bare | full state machine)

Supporting library code lives in pkg/service/setup: factory_reset.go,
wifi_provision.go, inspect.go, init_plan.go, setup_session.go.

Confirmed against ST10 firmware 27.0.6 that bare setMargeAccount over
WebSocket — no SETUP_START/SETUP_ENTER/SETUP_LEAVE bracket — is
sufficient to pair a factory-reset speaker; the firmware materializes
SystemConfigurationDB.xml and Sources.xml itself and the pairing
survives reboot. Result and field-by-field SystemConfigurationDB
comparison documented in docs/analysis/SETUP-WEBSOCKET-EXPERIMENT.md.
Captures the device's pre-reset DELETE-to-marge plus its LAN peer
notification flow in docs/analysis/FACTORY-RESET-PROTOCOL.md.

Perf: batch GetMigrationSummary's SSH probes into one Run() call via
ssh_probe.go / ssh_probe_apply.go — was ~8 sequential dials at
500-1000 ms each on FW 27 crypto, now one round-trip. Same data shape,
same MigrationSummary fields populated.

Fixes /clockTime and /clockDisplay wire formats — firmware 27 rejects
the legacy flat XML ("Error parsing request"). ClockTimeRequest now
uses utcTime attribute; ClockDisplayRequest emits the nested
<clockConfig> envelope with timezoneInfo/timeFormat/brightnessLevel.

Removes cmd/example-init-speaker (superseded by setup pair).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pkg/client/system_test.go

@@ -95,9 +95,7 @@ func TestClient_SetClockTime(t *testing.T) {
 		{
 			name: "Successful clock time set",
 			request: &models.ClockTimeRequest{
-				UTC:   1609459200,
-				Value: "2021-01-01 00:00:00",
-				Zone:  "UTC",
+				UTCTime: 1609459200,
 			},
 			statusCode:  http.StatusOK,
 			expectError: false,
@@ -112,8 +110,7 @@ func TestClient_SetClockTime(t *testing.T) {
 		{
 			name: "Server error",
 			request: &models.ClockTimeRequest{
-				UTC:   1609459200,
-				Value: "2021-01-01 00:00:00",
+				UTCTime: 1609459200,
 			},
 			statusCode:  http.StatusInternalServerError,
 			expectError: true,