[ADE-66] Enhance system prompt clarity and user prompt constraints in explainMedicalText method

[adamrefaey]

Change

• style: Improve SCSS formatting for better readability in AIAssistantModal and ProcessingPage

• feat: Add additional mock data for UploadModal in UploadPage tests

• fix: Enhance system prompt clarity and user prompt constraints in explainMedicalText method

Does this PR introduce a breaking change?

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What needs to be documented once your changes are merged?

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[Copilot]

Pull Request Overview

This PR improves the styling and clarity of the frontend and backend code related to UI tests, file uploads, and medical text explanation.

• Updated UploadPage test mock data with additional file attributes.
• Refactored ChatPage test component syntax for more concise JSX rendering.
• Enhanced system prompt and user prompt constraints and output formatting in the explainMedicalText method.

Reviewed Changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated no comments.

File	Description
frontend/src/pages/Upload/tests/UploadPage.test.tsx	Added additional mock data fields for better test coverage in UploadModal.
frontend/src/pages/Chat/tests/ChatPage.test.tsx	Streamlined the mock component function syntax for improved readability.
frontend/src/common/hooks/useFileUpload.ts	Minor formatting change in error message handling.
backend/src/services/perplexity.service.ts	Updated prompt text and added trim on response output for clarity and consistency.

Files not reviewed (2)

• frontend/src/common/components/AIAssistant/AIAssistantModal.scss: Language not supported
• frontend/src/pages/Processing/ProcessingPage.scss: Language not supported