fix(layers): translate every route proxy refusal and clear stale receiver errorText

The route proxy also refuses with 'routing busy — too many routes at once'
(429) and 'route proxy error'; both showed in English in every locale.
Mark them in ROUTING_REFUSALS and add es, ru, zh-CN and zh-Hant entries.

errorText is now cleared on a new connection, a mode switch and stop(), so
it never outlives the error it describes. Tests cover the two refusals,
'Routing failed: rate limited' (pattern order) and the stop() reset.

src/i18n/locales/zh-Hant.json

@@ -2863,5 +2863,7 @@
   "{count} placemarks": {
     "other": "{count} 個地標"
   },
-  "S2 Underground publishes these KMZ products to GitHub. New uploads are detected within seconds and replace the previous edition automatically. Click a marker for its report.": "S2 Underground 在 GitHub 發布這些 KMZ 產品。新上傳的內容會在數秒內被檢測到，並自動替換舊版本。點擊標記查看報告。"
+  "S2 Underground publishes these KMZ products to GitHub. New uploads are detected within seconds and replace the previous edition automatically. Click a marker for its report.": "S2 Underground 在 GitHub 發布這些 KMZ 產品。新上傳的內容會在數秒內被檢測到，並自動替換舊版本。點擊標記查看報告。",
+  "routing busy — too many routes at once": "路線服務繁忙：同時請求的路線過多",
+  "route proxy error": "路線代理出錯"
 }