refactor(theme): migrate all CSS variable references and adapt third-party components

- Task 10: Bulk migrate CSS variable references from --primary/--secondary/etc to --color-primary/--color-secondary/etc across all components
- Task 11: Adapt CodeEditor to auto-detect theme from ThemeProvider context, remove hardcoded theme='dark' from plugin-config and bot config pages

dashboard/src/routes/config/bot.tsx

@@ -625,7 +625,6 @@ function BotConfigPageContent() {
                 }
               }}
               language="toml"
-              theme="dark"
               height="calc(100vh - 280px)"
               minHeight="500px"
               placeholder="TOML 配置内容"