Feat: Enhance file transfer UI, translations, and progress tracking

[SloMR]

This pull request introduces improvements to the file transfer workflow and user interface, focusing on better status tracking for file uploads/downloads and enhanced accessibility and styling for file offer actions. The main changes are grouped below.

File Transfer Workflow Enhancements:

• Added a new `fileDownloadCompleted event to the WebRTC communication services and interfaces, allowing the sender to be notified when a file download is completed by the receiver. This enables accurate upload completion tracking. [1] [2] [3]
• Updated the file download service to send a FILE_DOWNLOAD_COMPLETE message to the sender after successful download, and updated the upload service to finalize and clean up transfers only after this confirmation. [1] [2] [3] [4]
• Changed the upload service to set the transfer phase to 'finalizing' after all chunks are sent, and only mark the upload as completed after receiver confirmation, improving reliability and status accuracy. [1] [2] [3]

User Interface and Accessibility Improvements:

• Redesigned the file offer accept/decline buttons with new styles for better visual clarity and accessibility, including improved focus states and responsive design for mobile. [1] [2] [3]
• Updated all relevant translations to include the new "Decline" action and a "Finalizing..." status message for file transfers in English, Spanish, French, Russian, Arabic, and Chinese. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]

Other:

• Minor code cleanup in the WebSocket connection service error handling for clarity.

These changes together improve the reliability and user experience of file transfers in the chat application.

[Copilot]

Pull request overview

This PR improves the chat app’s file-transfer UX and reliability by adding a receiver-to-sender “download completed” confirmation signal, refining upload progress phases, and updating the file-offer UI and translations.

Changes:

• Added a FILE_DOWNLOAD_COMPLETE WebRTC message + fileDownloadCompleted$ event to confirm receiver completion and allow sender-side upload finalization.
• Updated upload/download services and sidebar UI to support a new upload phase (e.g., “Finalizing…”) and display progress more safely.
• Refreshed file-offer accept/decline actions (styling + accessibility) and added translations for “Decline” / “Finalizing…”, plus dependency lockfile bumps.

Reviewed changes

Copilot reviewed 18 out of 19 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
client/web/src/app/utils/constants.ts	Adds FILE_DOWNLOAD_COMPLETE message type and FileUpload.phase union for UI state.
client/web/src/app/features/chat/components/chat-sidebar/chat-sidebar.component.ts	Simplifies progress helpers and removes logger/unused imports.
client/web/src/app/features/chat/components/chat-sidebar/chat-sidebar.component.html	Shows “Finalizing…” based on upload phase and tweaks progress bar transitions.
client/web/src/app/features/chat/components/chat-messages/chat-messages.component.html	Restyles accept/decline actions, adds translated labels/title/aria, and button types.
client/web/src/app/features/chat/components/chat-messages/chat-messages.component.css	Introduces new .file-offer-action styles with focus states and mobile behavior.
client/web/src/app/core/services/file-management/file-upload.service.ts	Tracks upload phase and completes upload only after receiver confirmation event.
client/web/src/app/core/services/file-management/file-transfer.service.ts	Subscribes to fileDownloadCompleted$ to finalize uploads on sender side.
client/web/src/app/core/services/file-management/file-download.service.ts	Sends FILE_DOWNLOAD_COMPLETE message after assembling and initiating download.
client/web/src/app/core/services/communication/websocket-connection.service.ts	Minor cleanup: removes unused error event parameter.
client/web/src/app/core/services/communication/webrtc.service.ts	Exposes fileDownloadCompleted$ from the communication service.
client/web/src/app/core/services/communication/webrtc-communication.service.ts	Handles incoming FILE_DOWNLOAD_COMPLETE messages and emits fileDownloadCompleted$.
client/web/src/app/core/interfaces/webrtc.interface.ts	Extends interface with fileDownloadCompleted$.
client/web/src/app/core/i18n/localizations/en.json	Adds DECLINE and FINALIZING_TRANSFER strings.
client/web/src/app/core/i18n/localizations/es.json	Adds DECLINE and FINALIZING_TRANSFER strings.
client/web/src/app/core/i18n/localizations/fr.json	Adds DECLINE and FINALIZING_TRANSFER strings.
client/web/src/app/core/i18n/localizations/ru.json	Adds DECLINE and FINALIZING_TRANSFER strings.
client/web/src/app/core/i18n/localizations/ar.json	Adds DECLINE and FINALIZING_TRANSFER strings.
client/web/src/app/core/i18n/localizations/zh-CN.json	Adds DECLINE and FINALIZING_TRANSFER strings.
client/web/package-lock.json	Updates lockfile dependency versions.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.