feat(i18n): extract hardcoded English strings to locale files (#1806)

* Extract hardcoded strings to i18n

Replace numerous hardcoded English strings with I18n lookups (t / I18n.t) across controllers, views, helpers, and components, and convert model validation error messages to symbol keys. Added multiple locale files under config/locales for models and views. This centralizes user-facing notices/alerts, UI text, import/validation messages, and prepares the app for localization and easier translation maintenance.

* Update en.yml

* Update preview-cleanup.yml

* Revert "Update preview-cleanup.yml"

This reverts commit 1ba6d3c34c.

* test: align i18n assertions with translated messages

* Standardize balance error key and tweak locales

Replace SophtronAccount's :requires_balance error key with :no_balance and update related locale strings for sophtron, plaid, and simplefin accounts to use the new key and clearer copy. Also switch the QIF upload redirect notice to use a relative translation key (t('.qif_uploaded')), remove an unused SSO providers help line, and fix a trailing-newline/whitespace issue in the subscriptions locale. These changes standardize validation keys and improve translation consistency and messaging.

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Co-authored-by: KiloClaw <kiloclaw@openclaw.ai>

app/views/chats/_error.html.erb

@@ -11,7 +11,7 @@
     <p class="text-xs text-red-500"><%= chat.presentable_error_message %></p>
 
     <%= render DS::Button.new(
-      text: "Retry",
+      text: t(".retry"),
       href: retry_chat_path(chat),
     ) %>
   </div>