feat(mcp): add overwrite warning and improve sync option visibility

- Move sync checkbox to footer alongside save/cancel buttons for better visibility
- Add real-time conflict detection to check for duplicate MCP IDs on other side
- Display amber warning icon when sync would overwrite existing config
- Add i18n keys for overwrite warning (zh: "将覆盖 {{target}} 中的同名配置")
- Update UI layout to use justify-between for better spacing

src/i18n/locales/en.json

@@ -300,7 +300,8 @@
       "tomlPlaceholder": "type = \"stdio\"\ncommand = \"uvx\"\nargs = [\"mcp-server-fetch\"]",
       "useWizard": "Config Wizard",
       "syncOtherSide": "Mirror to {{target}}",
-      "syncOtherSideHint": "Apply the same settings to {{target}}; existing entries with the same id will be overwritten."
+      "syncOtherSideHint": "Apply the same settings to {{target}}; existing entries with the same id will be overwritten.",
+      "willOverwriteWarning": "Will overwrite existing config in {{target}}"
     },
     "wizard": {
       "title": "MCP Configuration Wizard",

src/i18n/locales/zh.json

@@ -300,7 +300,8 @@
       "tomlPlaceholder": "type = \"stdio\"\ncommand = \"uvx\"\nargs = [\"mcp-server-fetch\"]",
       "useWizard": "配置向导",
       "syncOtherSide": "同步到 {{target}}",
-      "syncOtherSideHint": "勾选后会把当前配置同时写入 {{target}}，若存在同名配置将被覆盖"
+      "syncOtherSideHint": "勾选后会把当前配置同时写入 {{target}}，若存在同名配置将被覆盖",
+      "willOverwriteWarning": "将覆盖 {{target}} 中的同名配置"
     },
     "wizard": {
       "title": "MCP 配置向导",