feat(travel): Implement settings UI and web server for MTR route configuration

- Added MainUIHandler class to manage the main UI and polling for arrival data.
- Introduced SettingsUI class for displaying QR code and configuration options.
- Created SettingsUIHandler to manage settings UI lifecycle and web server interactions.
- Developed WebHandler to handle HTTP requests for MTR route settings, including adding and removing routes.
- Implemented web endpoints for fetching MTR lines, routes, and saving settings.
- Enhanced UI with responsive design for e-ink displays and added error handling for web interactions.

main/ui/apps/travel/settings/settings_handler.cpp

@@ -0,0 +1,170 @@
+#include "ui/apps/travel/settings/settings_handler.h"
+#include "cJSON.h"
+#include "esp_log.h"
+
+static const char* TAG = "TravelSettings";
+
+namespace travel {
+
+SettingHandler::SettingHandler(std::unique_ptr<NVSStorageHandler> storage)
+  : routes_()
+  , polling_interval_sec_(DEFAULT_POLLING_INTERVAL)
+  , storage_(std::move(storage)) {
+}
+
+esp_err_t SettingHandler::init(const EventGroupHandle_t& system_event_group) {
+  storage_->init(system_event_group);
+  return ESP_OK;
+}
+
+void SettingHandler::load_settings() {
+  // Load polling interval
+  std::string poll_str = storage_->get(NVS_KEY_POLLING);
+  if (!poll_str.empty()) {
+    polling_interval_sec_ = std::stoul(poll_str);
+    if (polling_interval_sec_ < MIN_POLLING_INTERVAL ||
+        polling_interval_sec_ > MAX_POLLING_INTERVAL) {
+      polling_interval_sec_ = DEFAULT_POLLING_INTERVAL;
+    }
+  }
+
+  // Load routes
+  std::string routes_json = storage_->get(NVS_KEY_ROUTES);
+  if (!routes_json.empty()) {
+    routes_from_json(routes_json);
+  }
+
+  ESP_LOGI(TAG, "Loaded %d routes, polling interval: %d seconds",
+           static_cast<int>(routes_.size()), static_cast<int>(polling_interval_sec_));
+}
+
+void SettingHandler::save_settings() {
+  // Save polling interval
+  storage_->put(NVS_KEY_POLLING, std::to_string(polling_interval_sec_));
+
+  // Save routes
+  std::string routes_json = routes_to_json();
+  storage_->put(NVS_KEY_ROUTES, routes_json);
+
+  ESP_LOGI(TAG, "Saved %d routes, polling interval: %d seconds",
+           static_cast<int>(routes_.size()), static_cast<int>(polling_interval_sec_));
+}
+
+void SettingHandler::add_route(const RoutePair& route) {
+  if (routes_.size() >= MAX_ROUTES) {
+    ESP_LOGW(TAG, "Maximum number of routes reached (%d)", static_cast<int>(MAX_ROUTES));
+    return;
+  }
+
+  // Check for duplicates
+  for (const auto& existing : routes_) {
+    if (existing == route) {
+      ESP_LOGW(TAG, "Route already exists");
+      return;
+    }
+  }
+
+  routes_.push_back(route);
+  ESP_LOGI(TAG, "Added route: %s -> %s", route.station_name.c_str(), route.dest_name.c_str());
+}
+
+void SettingHandler::remove_route(size_t index) {
+  if (index < routes_.size()) {
+    ESP_LOGI(TAG, "Removing route at index %d", static_cast<int>(index));
+    routes_.erase(routes_.begin() + index);
+  }
+}
+
+void SettingHandler::clear_routes() {
+  routes_.clear();
+  ESP_LOGI(TAG, "Cleared all routes");
+}
+
+void SettingHandler::set_polling_interval(uint32_t seconds) {
+  if (seconds < MIN_POLLING_INTERVAL) {
+    seconds = MIN_POLLING_INTERVAL;
+  } else if (seconds > MAX_POLLING_INTERVAL) {
+    seconds = MAX_POLLING_INTERVAL;
+  }
+  polling_interval_sec_ = seconds;
+  ESP_LOGI(TAG, "Set polling interval to %d seconds", static_cast<int>(seconds));
+}
+
+std::string SettingHandler::routes_to_json() const {
+  cJSON* root = cJSON_CreateArray();
+
+  for (const auto& route : routes_) {
+    cJSON* route_obj = cJSON_CreateObject();
+    cJSON_AddStringToObject(route_obj, "line_code", route.line_code.c_str());
+    cJSON_AddStringToObject(route_obj, "line_name", route.line_name.c_str());
+    cJSON_AddStringToObject(route_obj, "line_color", route.line_color.c_str());
+    cJSON_AddStringToObject(route_obj, "station_code", route.station_code.c_str());
+    cJSON_AddStringToObject(route_obj, "station_name", route.station_name.c_str());
+    cJSON_AddStringToObject(route_obj, "dest_code", route.dest_code.c_str());
+    cJSON_AddStringToObject(route_obj, "dest_name", route.dest_name.c_str());
+    cJSON_AddItemToArray(root, route_obj);
+  }
+
+  char* json_str = cJSON_PrintUnformatted(root);
+  std::string result(json_str ? json_str : "[]");
+  if (json_str) {
+    free(json_str);
+  }
+  cJSON_Delete(root);
+
+  return result;
+}
+
+void SettingHandler::routes_from_json(const std::string& json) {
+  routes_.clear();
+
+  cJSON* root = cJSON_Parse(json.c_str());
+  if (!root || !cJSON_IsArray(root)) {
+    ESP_LOGE(TAG, "Failed to parse routes JSON");
+    if (root) {
+      cJSON_Delete(root);
+    }
+    return;
+  }
+
+  int array_size = cJSON_GetArraySize(root);
+  for (int i = 0; i < array_size && i < static_cast<int>(MAX_ROUTES); i++) {
+    cJSON* route_obj = cJSON_GetArrayItem(root, i);
+    if (!route_obj || !cJSON_IsObject(route_obj)) {
+      continue;
+    }
+
+    RoutePair route;
+    cJSON* item;
+
+    item = cJSON_GetObjectItem(route_obj, "line_code");
+    if (item && cJSON_IsString(item)) route.line_code = item->valuestring;
+
+    item = cJSON_GetObjectItem(route_obj, "line_name");
+    if (item && cJSON_IsString(item)) route.line_name = item->valuestring;
+
+    item = cJSON_GetObjectItem(route_obj, "line_color");
+    if (item && cJSON_IsString(item)) route.line_color = item->valuestring;
+
+    item = cJSON_GetObjectItem(route_obj, "station_code");
+    if (item && cJSON_IsString(item)) route.station_code = item->valuestring;
+
+    item = cJSON_GetObjectItem(route_obj, "station_name");
+    if (item && cJSON_IsString(item)) route.station_name = item->valuestring;
+
+    item = cJSON_GetObjectItem(route_obj, "dest_code");
+    if (item && cJSON_IsString(item)) route.dest_code = item->valuestring;
+
+    item = cJSON_GetObjectItem(route_obj, "dest_name");
+    if (item && cJSON_IsString(item)) route.dest_name = item->valuestring;
+
+    if (!route.line_code.empty() && !route.station_code.empty() && !route.dest_code.empty()) {
+      routes_.push_back(route);
+    }
+  }
+
+  cJSON_Delete(root);
+  ESP_LOGI(TAG, "Loaded %d routes from JSON", static_cast<int>(routes_.size()));
+}
+
+} // namespace travel