fix(i18n): complete zh_TW locale coverage (#13792)

This updates the Traditional Chinese (`zh_TW`) locale coverage across
Chatwoot so the app no longer falls back to English for missing backend,
dashboard, widget, and survey strings.

## How to test

1. Start Chatwoot locally and switch the UI locale to Traditional
Chinese (`zh_TW`).
2. Walk through the main product areas: dashboard, settings, inbox
management, help center, automations, reports, widget, and survey flows.
3. Confirm the UI surfaces translated Traditional Chinese copy instead
of English fallbacks.
4. Spot-check newly added locale surfaces such as secure password
messaging and snooze UI copy.

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

app/javascript/survey/i18n/locale/zh_TW.json

@@ -7,7 +7,7 @@
     },
     "FEEDBACK": {
       "LABEL": "有什麼想法想分享嗎？",
-      "PLACEHOLDER": "Your feedback (optional)",
+      "PLACEHOLDER": "您的反饋(可選)",
       "BUTTON_TEXT": "提交反饋"
     },
     "API": {
@@ -15,5 +15,5 @@
       "ERROR_MESSAGE": "無法連接伺服器，請稍後再試"
     }
   },
-  "POWERED_BY": "Powered by Chatwoot"
+  "POWERED_BY": "由 Chatwoot 支援"
 }