feat: 添加时区设置功能，默认时区改为 CST-8

- 新增 set_timezone LLM 工具，支持通过对话设置时区
- 新增 set_timezone / timezone_show CLI 命令
- 默认时区从 PST 改为 CST-8（中国标准时间 UTC+8）
- 支持 POSIX 格式和 18 个城市名映射（Asia/Shanghai 等）
- 时区通过 NVS 持久化存储（system_config namespace）
- config_show 中显示当前时区配置
- 更新 changelog.md 和 taolun.md 文档

main/onboard/onboard_html.h

@@ -56,10 +56,14 @@ static const char ONBOARD_HTML[] =
 "<label>Model</label>"
 "<input id='model' placeholder='claude-opus-4-5' value='claude-opus-4-5'>"
 "<label>Provider</label>"
-"<select id='provider'>"
+"<select id='provider' onchange='onProviderChange()'>"
 "<option value='anthropic'>Anthropic</option>"
 "<option value='openai'>OpenAI</option>"
+"<option value='siliconflow'>SiliconFlow (硅基流动)</option>"
+"<option value='volcengine'>Volcengine (火山引擎)</option>"
 "</select>"
+"<label>Base URL</label>"
+"<input id='base_url' placeholder='https://api.example.com/v1'>"
 "</div></div>"
 
 /* Telegram section */
@@ -133,8 +137,15 @@ static const char ONBOARD_HTML[] =
 "btn.textContent='Scan WiFi Networks';btn.disabled=false;"
 "}).catch(()=>{btn.textContent='Scan WiFi Networks';btn.disabled=false})}"
 
+"function onProviderChange(){"
+"var p=document.getElementById('provider').value;"
+"var u=document.getElementById('base_url');"
+"if(p==='siliconflow'){u.value='https://api.siliconflow.cn/v1'}"
+"else if(p==='volcengine'){u.value='https://ark.cn-beijing.volces.com/api/v3'}"
+"else{u.value=''}}"
+
 "function save(){"
-"var fields=['ssid','password','api_key','model','provider','tg_token',"
+"var fields=['ssid','password','api_key','model','provider','base_url','tg_token',"
 "'feishu_app_id','feishu_app_secret','proxy_host','proxy_port','proxy_type','search_key','tavily_key'];"
 "var data={};"
 "fields.forEach(f=>{data[f]=document.getElementById(f).value.trim()});"

main/onboard/wifi_onboard.c

@@ -220,6 +220,40 @@ static esp_err_t http_get_config(httpd_req_t *req)
     json_add_effective_config(root, "api_key", MIMI_NVS_LLM, MIMI_NVS_KEY_API_KEY, MIMI_SECRET_API_KEY);
     json_add_effective_config(root, "model", MIMI_NVS_LLM, MIMI_NVS_KEY_MODEL, MIMI_SECRET_MODEL);
     json_add_effective_config(root, "provider", MIMI_NVS_LLM, MIMI_NVS_KEY_PROVIDER, MIMI_SECRET_MODEL_PROVIDER);
+
+    /* Provider-specific Base URL (load from current provider's NVS key) */
+    {
+        char base_url[256] = {0};
+        bool found = false;
+        char provider[32] = {0};
+        nvs_handle_t nvs;
+        if (nvs_open(MIMI_NVS_LLM, NVS_READONLY, &nvs) == ESP_OK) {
+            size_t len = sizeof(provider);
+            if (nvs_get_str(nvs, MIMI_NVS_KEY_PROVIDER, provider, &len) != ESP_OK || !provider[0]) {
+                /* Fall back to build-time provider if NVS doesn't have one */
+                strlcpy(provider, MIMI_SECRET_MODEL_PROVIDER, sizeof(provider));
+            }
+            /* Try to load provider-specific base URL from NVS */
+            const char *url_key = NULL;
+            if (strcmp(provider, "anthropic") == 0) url_key = MIMI_NVS_KEY_ANTHROPIC_BASE_URL;
+            else if (strcmp(provider, "openai") == 0) url_key = MIMI_NVS_KEY_OPENAI_BASE_URL;
+            else if (strcmp(provider, "siliconflow") == 0) url_key = MIMI_NVS_KEY_SILICONFLOW_BASE_URL;
+            else if (strcmp(provider, "volcengine") == 0) url_key = MIMI_NVS_KEY_VOLCENGINE_BASE_URL;
+            if (url_key) {
+                len = sizeof(base_url);
+                if (nvs_get_str(nvs, url_key, base_url, &len) == ESP_OK && base_url[0]) {
+                    found = true;
+                }
+            }
+            nvs_close(nvs);
+        }
+        if (!found) {
+            /* Fall back to build-time defaults */
+            if (strcmp(provider, "siliconflow") == 0) strlcpy(base_url, MIMI_SECRET_SILICONFLOW_BASE_URL, sizeof(base_url));
+            else if (strcmp(provider, "volcengine") == 0) strlcpy(base_url, MIMI_SECRET_VOLCENGINE_BASE_URL, sizeof(base_url));
+        }
+        cJSON_AddStringToObject(root, "base_url", base_url);
+    }
     json_add_effective_config(root, "tg_token", MIMI_NVS_TG, MIMI_NVS_KEY_TG_TOKEN, MIMI_SECRET_TG_TOKEN);
     json_add_effective_config(root, "feishu_app_id", MIMI_NVS_FEISHU, MIMI_NVS_KEY_FEISHU_APP_ID, MIMI_SECRET_FEISHU_APP_ID);
     json_add_effective_config(root, "feishu_app_secret", MIMI_NVS_FEISHU, MIMI_NVS_KEY_FEISHU_APP_SECRET, MIMI_SECRET_FEISHU_APP_SECRET);
@@ -344,6 +378,37 @@ static esp_err_t http_post_save(httpd_req_t *req)
     nvs_sync_field(root, "model",    MIMI_NVS_LLM,    MIMI_NVS_KEY_MODEL);
     nvs_sync_field(root, "provider", MIMI_NVS_LLM,    MIMI_NVS_KEY_PROVIDER);
 
+    /* Save API key and base URL to provider-specific NVS keys */
+    {
+        cJSON *provider_item = cJSON_GetObjectItem(root, "provider");
+        cJSON *api_key_item = cJSON_GetObjectItem(root, "api_key");
+        cJSON *base_url_item = cJSON_GetObjectItem(root, "base_url");
+        if (provider_item && cJSON_IsString(provider_item) && provider_item->valuestring[0]) {
+            const char *provider = provider_item->valuestring;
+            const char *api_key_nvs = NULL;
+            const char *base_url_nvs = NULL;
+            if (strcmp(provider, "anthropic") == 0) {
+                api_key_nvs = MIMI_NVS_KEY_ANTHROPIC_API_KEY;
+                base_url_nvs = MIMI_NVS_KEY_ANTHROPIC_BASE_URL;
+            } else if (strcmp(provider, "openai") == 0) {
+                api_key_nvs = MIMI_NVS_KEY_OPENAI_API_KEY;
+                base_url_nvs = MIMI_NVS_KEY_OPENAI_BASE_URL;
+            } else if (strcmp(provider, "siliconflow") == 0) {
+                api_key_nvs = MIMI_NVS_KEY_SILICONFLOW_API_KEY;
+                base_url_nvs = MIMI_NVS_KEY_SILICONFLOW_BASE_URL;
+            } else if (strcmp(provider, "volcengine") == 0) {
+                api_key_nvs = MIMI_NVS_KEY_VOLCENGINE_API_KEY;
+                base_url_nvs = MIMI_NVS_KEY_VOLCENGINE_BASE_URL;
+            }
+            if (api_key_nvs && api_key_item && cJSON_IsString(api_key_item)) {
+                nvs_sync_field(root, "api_key", MIMI_NVS_LLM, api_key_nvs);
+            }
+            if (base_url_nvs && base_url_item && cJSON_IsString(base_url_item)) {
+                nvs_sync_field(root, "base_url", MIMI_NVS_LLM, base_url_nvs);
+            }
+        }
+    }
+
     /* Telegram */
     nvs_sync_field(root, "tg_token", MIMI_NVS_TG,     MIMI_NVS_KEY_TG_TOKEN);