feat: Validates file types before upload

Prevents uploading of unsupported file types to the chat.

Displays an alert message to the user when attempting to upload
unsupported files, informing them about the acceptable file formats.
Only processes supported files, improving the user experience.

Author: allozaur

tools/server/webui/src/lib/components/app/chat/ChatScreen/ChatScreen.svelte

@@ -2,6 +2,7 @@
 	import { parseFilesToMessageExtras } from '$lib/utils/convert-files-to-extra';
 	import { processFilesToChatUploaded } from '$lib/utils/process-uploaded-files';
 	import { serverStore } from '$lib/stores/server.svelte';
+	import { isFileTypeSupported } from '$lib/constants/supported-file-types';
 	import { ChatForm, ChatScreenHeader, ChatMessages, ServerInfo } from '$lib/components/app';
 	import {
 		activeMessages,
@@ -116,8 +117,30 @@
 	}
 
 	async function processFiles(files: File[]) {
-		const processed = await processFilesToChatUploaded(files);
-		uploadedFiles = [...uploadedFiles, ...processed];
+		const supportedFiles: File[] = [];
+		const unsupportedFiles: File[] = [];
+
+		for (const file of files) {
+			if (isFileTypeSupported(file.name, file.type)) {
+				supportedFiles.push(file);
+			} else {
+				unsupportedFiles.push(file);
+			}
+		}
+
+		if (unsupportedFiles.length > 0) {
+			const fileNames = unsupportedFiles.map(f => f.name).join(', ');
+			const message = unsupportedFiles.length === 1 
+				? `The file "${fileNames}" is not supported. Please upload images (JPG, PNG, GIF, WebP, SVG), audio files (MP3, WAV), PDFs, or text files.`
+				: `The following files are not supported: ${fileNames}. Please upload images (JPG, PNG, GIF, WebP, SVG), audio files (MP3, WAV), PDFs, or text files.`;
+			
+			alert(message);
+		}
+
+		if (supportedFiles.length > 0) {
+			const processed = await processFilesToChatUploaded(supportedFiles);
+			uploadedFiles = [...uploadedFiles, ...processed];
+		}
 	}
 
 	function scrollChatToBottom(behavior: ScrollBehavior = 'smooth') {