Fix: prevent infinite loading on identical language translation

[Reckz69]

fix: #1488
This PR improves the translation plugin by implementing a validation check that prevents initiating a process when source and target languages are identical. Previously, this triggered an infinite loading spinner and a confusing UI state. This update replaces the indefinite loading state with a direct user-facing error and cleans up redundant UI warnings, ensuring more robust state management and a better UX.

[Reckz69]

This update improves the translation plugin’s behavior when the selected source and target languages are the same.

Changes

• Added a validation check to prevent translation from starting if the source and target languages match.

• Displays a user-facing error instead of entering a loading state.

• Prevents the language model spinner from running indefinitely in this scenario.

• Removed the redundant “same language” warning text from the panel UI.

Reason

Previously, initiating translation with identical languages caused the UI to enter a loading state without performing any action, leading to confusing UX and an endless spinner. This fix ensures proper validation, clearer feedback, and consistent UI state management.