fix(wiki): monochrome icon for the New wiki source option

The add-source grid inverts black icons to white (dark:invert), but the wiki used book.svg (fill #6A4DF4), which inverted to lime. Point the wiki ingestor at a new black book-mono.svg so it renders white like the others; book.svg stays purple for its other use (PromptsModal, no invert there).

frontend/src/assets/book-mono.svg

@@ -0,0 +1,3 @@
+<svg width="12" height="14" viewBox="0 0 12 14" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M10.2857 14H2.57143C1.15179 14 0 12.8242 0 11.375V2.625C0 1.17578 1.15179 0 2.57143 0H10.7143C11.4241 0 12 0.587891 12 1.3125V9.1875C12 9.75898 11.6411 10.2457 11.1429 10.4262V12.25C11.617 12.25 12 12.641 12 13.125C12 13.609 11.617 14 11.1429 14H10.2857ZM2.57143 10.5C2.09732 10.5 1.71429 10.891 1.71429 11.375C1.71429 11.859 2.09732 12.25 2.57143 12.25H9.42857V10.5H2.57143ZM3.42857 4.15625C3.42857 4.51992 3.71518 4.8125 4.07143 4.8125H8.78571C9.14196 4.8125 9.42857 4.51992 9.42857 4.15625C9.42857 3.79258 9.14196 3.5 8.78571 3.5H4.07143C3.71518 3.5 3.42857 3.79258 3.42857 4.15625ZM4.07143 6.125C3.71518 6.125 3.42857 6.41758 3.42857 6.78125C3.42857 7.14492 3.71518 7.4375 4.07143 7.4375H8.78571C9.14196 7.4375 9.42857 7.14492 9.42857 6.78125C9.42857 6.41758 9.14196 6.125 8.78571 6.125H4.07143Z" fill="black"/>
+</svg>

frontend/src/upload/types/ingestor.ts

@@ -7,7 +7,7 @@ import DriveIcon from '../../assets/drive.svg';
 import S3Icon from '../../assets/s3.svg';
 import SharePoint from '../../assets/sharepoint.svg';
 import ConfluenceIcon from '../../assets/confluence.svg';
-import BookIcon from '../../assets/book.svg';
+import BookIcon from '../../assets/book-mono.svg';
 
 export type IngestorType =
   | 'confluence'