refactor: Refactors file type handling using enums

Centralizes and strengthens file type management by using enums for categories, MIME types, and extensions.

This improves code maintainability and type safety when dealing with different file types across the application.
It also enforces a consistent approach for file type detection.

Author: allozaur

tools/server/webui/src/lib/components/app/chat/ChatAttachments/ChatAttachmentPreviewDialog.svelte

@@ -3,6 +3,7 @@
 	import { FileText, Image, Music, FileIcon, Eye } from '@lucide/svelte';
 	import { convertPDFToImage } from '$lib/utils/pdf-processing';
 	import { Button } from '$lib/components/ui/button';
+	import { FileTypeCategory, PdfMimeType, getFileTypeCategory } from '$lib/constants/supported-file-types';
 
 	interface Props {
 		open: boolean;
@@ -59,10 +60,10 @@
 					: textContent)
 	);
 
-	let isImage = $derived(displayType.startsWith('image/') || displayType === 'image');
-	let isText = $derived(displayType.startsWith('text/') || displayType === 'text');
-	let isPdf = $derived(displayType === 'application/pdf');
-	let isAudio = $derived(displayType.startsWith('audio/') || displayType === 'audio');
+	let isImage = $derived(getFileTypeCategory(displayType) === FileTypeCategory.IMAGE || displayType === 'image');
+	let isText = $derived(getFileTypeCategory(displayType) === FileTypeCategory.TEXT || displayType === 'text');
+	let isPdf = $derived(displayType === PdfMimeType.PDF);
+	let isAudio = $derived(getFileTypeCategory(displayType) === FileTypeCategory.AUDIO || displayType === 'audio');
 
 	// PDF preview state
 	let pdfViewMode = $state<'text' | 'pages'>('pages'); // Default to pages view
@@ -120,7 +121,7 @@
 						byteNumbers[i] = byteCharacters.charCodeAt(i);
 					}
 					const byteArray = new Uint8Array(byteNumbers);
-					file = new File([byteArray], displayName, { type: 'application/pdf' });
+					file = new File([byteArray], displayName, { type: PdfMimeType.PDF });
 					if (import.meta.env.DEV) console.log('Created file from base64 data, size:', file.size);
 				}
 			}

tools/server/webui/src/lib/components/app/chat/ChatAttachments/ChatAttachmentsList.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
 	import { ChatAttachmentImagePreview, ChatAttachmentFilePreview } from '$lib/components/app';
 	import ChatAttachmentPreviewDialog from './ChatAttachmentPreviewDialog.svelte';
+	import { FileTypeCategory, PdfMimeType, getFileTypeCategory } from '$lib/constants/supported-file-types';
 
 	interface Props {
 		class?: string;
@@ -77,7 +78,7 @@
 				size: file.size,
 				preview: file.preview,
 				type: file.type,
-				isImage: file.type.startsWith('image/'),
+				isImage: getFileTypeCategory(file.type) === FileTypeCategory.IMAGE,
 				uploadedFile: file,
 				textContent: file.textContent
 			});

tools/server/webui/src/lib/components/app/chat/ChatForm/ChatFormFileInputInvisible.svelte

@@ -1,13 +1,21 @@
 <script lang="ts">
+	import { ALL_SUPPORTED_EXTENSIONS, ALL_SUPPORTED_MIME_TYPES } from '$lib/constants/supported-file-types';
+
 	interface Props {
 		accept?: string;
 		multiple?: boolean;
 		onFileSelect?: (files: File[]) => void;
 		class?: string;
 	}
 
+	// Generate accept string from our enum-based supported file types
+	const defaultAccept = [
+		...ALL_SUPPORTED_EXTENSIONS,
+		...ALL_SUPPORTED_MIME_TYPES,
+	].join(',');
+
 	let {
-		accept = "image/*,audio/*,video/*,.pdf,.txt,.doc,.docx",
+		accept = defaultAccept,
 		multiple = true,
 		onFileSelect,
 		class: className = ''