Start keeping lock switch polarity in nvs

i will use this to do a sneaky trick; in-place upgrading brendan,
hailey, and erin's devices

src/drivers/include/nvs.hpp

@@ -22,6 +22,9 @@ class NvsStorage {
  public:
   static auto OpenSync() -> NvsStorage*;
 
+  auto LockPolarity() -> bool;
+  auto LockPolarity(bool) -> bool;
+
   auto PreferredBluetoothDevice() -> std::optional<bluetooth::mac_addr_t>;
   auto PreferredBluetoothDevice(std::optional<bluetooth::mac_addr_t>) -> bool;
 

src/drivers/nvs.cpp

@@ -33,6 +33,7 @@ static constexpr char kKeyAmpCurrentVolume[] = "hp_vol";
 static constexpr char kKeyAmpLeftBias[] = "hp_bias";
 static constexpr char kKeyOnboarded[] = "intro";
 static constexpr char kKeyPrimaryInput[] = "in_pri";
+static constexpr char kKeyLockPolarity[] = "lockpol";
 
 auto NvsStorage::OpenSync() -> NvsStorage* {
   esp_err_t err = nvs_flash_init();
@@ -85,6 +86,19 @@ auto NvsStorage::SchemaVersionSync() -> uint8_t {
   return ret;
 }
 
+auto NvsStorage::LockPolarity() -> bool {
+  uint8_t res;
+  if (nvs_get_u8(handle_, kKeyLockPolarity, &res) != ESP_OK) {
+    return false;
+  }
+  return res > 0;
+}
+
+auto NvsStorage::LockPolarity(bool p) -> bool {
+  nvs_set_u8(handle_, kKeyLockPolarity, p);
+  return nvs_commit(handle_) == ESP_OK;
+}
+
 auto NvsStorage::PreferredBluetoothDevice()
     -> std::optional<bluetooth::mac_addr_t> {
   bluetooth::mac_addr_t out{0};

src/system_fsm/booting.cpp

@@ -98,6 +98,8 @@ auto Booting::entry() -> void {
     sServices->bluetooth().Enable();
   }
 
+  sServices->nvs().LockPolarity(true);
+
   BootComplete ev{.services = sServices};
   events::Audio().Dispatch(ev);
   events::Ui().Dispatch(ev);