feat(mcp): unify modal styles and add footer with done button

- Unify McpFormModal width to max-w-3xl (consistent with provider form)
- Add scrollable container with max-h-[90vh] to McpFormModal
- Add footer section to both McpFormModal and McpPanel
- Add "Done" button with emerald theme and check icon to McpPanel footer
- Add i18n keys for "common.done" (zh: "完成", en: "Done")
- Apply consistent footer styling across all modals

src/i18n/locales/en.json

@@ -12,6 +12,7 @@
     "cancel": "Cancel",
     "confirm": "Confirm",
     "close": "Close",
+    "done": "Done",
     "settings": "Settings",
     "about": "About",
     "version": "Version",