feat: 添加编译时模块开关配置

通过 sdkconfig.defaults 选择性启用/禁用模块，减少固件体积：

新增模块开关：
- CONFIG_MIMI_CHAN_TELEGRAM (默认 n)
- CONFIG_MIMI_CHAN_FEISHU (默认 y)
- CONFIG_MIMI_TOOL_WEB_SEARCH (默认 y)
- CONFIG_MIMI_TOOL_GPIO (默认 n)
- CONFIG_MIMI_WS_SERVER (默认 y)
- CONFIG_MIMI_WIFI_ONBOARD (默认 y)
- CONFIG_MIMI_OTA (默认 n)

技术实现：
- CMakeLists.txt 条件编译源文件
- 头文件使用 static inline stub
- CLI 命令和工具注册也支持条件编译

消除 Telegram 未配置时的 5 秒轮询警告日志

main/channels/telegram/telegram_bot.h

@@ -2,26 +2,20 @@
 
 #include "esp_err.h"
 
-/**
- * Initialize the Telegram bot.
- */
+#ifdef CONFIG_MIMI_CHAN_TELEGRAM
 esp_err_t telegram_bot_init(void);
-
-/**
- * Start the Telegram polling task (long polling on Core 0).
- */
 esp_err_t telegram_bot_start(void);
-
-/**
- * Send a text message to a Telegram chat.
- * Automatically splits messages longer than 4096 chars.
- * @param chat_id  Telegram chat ID (numeric string)
- * @param text     Message text (supports Markdown)
- */
 esp_err_t telegram_send_message(const char *chat_id, const char *text);
-
-/**
- * Save the Telegram bot token to NVS.
- */
 esp_err_t telegram_set_token(const char *token);
-
+#else
+static inline esp_err_t telegram_bot_init(void) { return ESP_OK; }
+static inline esp_err_t telegram_bot_start(void) { return ESP_OK; }
+static inline esp_err_t telegram_send_message(const char *chat_id, const char *text) {
+    (void)chat_id; (void)text;
+    return ESP_OK;
+}
+static inline esp_err_t telegram_set_token(const char *token) {
+    (void)token;
+    return ESP_OK;
+}
+#endif