feat(i18n): English localization (phase 3)

- Translate content to English across messages/en.json, data/en, lib/data/en, and public/exemplos/en
- Implement localized routing, slugs, and language negotiation with fallback to en
- Build dedicated search index for English with strict book exclusion
- Update components and pages to dynamically render localized strings and datasets
- Verify full structural parity and exact 1:1 match on Portuguese pages via comparator

Co-Authored-By: Antigravity <noreply@google.com>

public/exemplos/en/esp-matter.c

@@ -0,0 +1,44 @@
+#include <stdio.h>
+#include "esp_log.h"
+#include "esp_matter.h"
+#include "esp_matter_controller.h"
+#include "nvs_flash.h"
+
+static const char *TAG = "esp-matter-example";
+
+void app_event_cb(const esp_matter_event_t *event)
+{
+    switch (event->event_id) {
+        case ESP_MATTER_EVENT_ATTRIBUTE_UPDATE: {
+            const esp_matter_attr_update_t *attr_update = &event->data.attr_update;
+            if (attr_update->endpoint_id == 1 && attr_update->cluster_id == ESP_MATTER_ON_OFF_CLUSTER_ID) {
+                bool on = false;
+                esp_matter_attribute_get(attr_update->endpoint_id, attr_update->cluster_id,
+                                         attr_update->attribute_id, &on);
+                ESP_LOGI(TAG, "Lâmpada %s", on ? "ligada" : "desligada");
+            }
+            break;
+        }
+        default:
+            break;
+    }
+}
+
+void app_main(void)
+{
+    // Inicializa NVS
+    esp_err_t err = nvs_flash_init();
+    if (err == ESP_ERR_NVS_NO_FREE_PAGES || err == ESP_ERR_NVS_NEW_VERSION_FOUND) {
+        ESP_ERROR_CHECK(nvs_flash_erase());
+        ESP_ERROR_CHECK(nvs_flash_init());
+    }
+
+    // Inicializa o Matter node
+    esp_matter::node_t *node = esp_matter::node::create(NULL, app_event_cb);
+    esp_matter::endpoint_t *endpoint = esp_matter::endpoint::create(node, ESP_MATTER_ENDPOINT_TYPE_ON_OFF_LIGHT);
+
+    // Inicia o stack Matter
+    ESP_ERROR_CHECK(esp_matter::start(node));
+
+    ESP_LOGI(TAG, "Dispositivo Matter iniciado. Aguardando comissionamento...");
+}