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

sdkconfig.defaults

@@ -6,3 +6,23 @@ CONFIG_LWIP_LOCAL_HOSTNAME="mimiclaw"
 
 # SPIFFS: increase max filename length (default 32 is too short for session files)
 CONFIG_SPIFFS_OBJ_NAME_LEN=64
+
+# ─── Channel Modules ──────────────────────────────────────────────
+# Telegram bot integration (disable if using Feishu only)
+CONFIG_MIMI_CHAN_TELEGRAM=n
+# Feishu (Lark) bot integration (default: enabled)
+CONFIG_MIMI_CHAN_FEISHU=y
+
+# ─── Tool Modules ─────────────────────────────────────────────────
+# Web search tool (requires search API key)
+CONFIG_MIMI_TOOL_WEB_SEARCH=y
+# GPIO control tool (for hardware control)
+CONFIG_MIMI_TOOL_GPIO=n
+
+# ─── Optional Modules ──────────────────────────────────────────────
+# WebSocket gateway (for local clients)
+CONFIG_MIMI_WS_SERVER=y
+# WiFi onboarding portal (Captive Portal for initial setup)
+CONFIG_MIMI_WIFI_ONBOARD=y
+# OTA firmware update (not fully implemented)
+CONFIG_MIMI_OTA=n