refactor(import): remove non-functional DOCX/PDF/Confluence import buttons

DOCX, PDF and Confluence import relied on a private EE module that was
dropped from this build, so those code paths only threw "enterprise
license" errors (DOCX/PDF) or silently did nothing (Confluence) while the
UI still presented them as working options.

- page-import-modal: drop the Word (DOCX), PDF and Confluence FileButtons
- remove the now-dead icon imports (IconFileTypeDocx, IconFileTypePdf,
  ConfluenceIcon), the docx/pdf/confluence file refs and their input-reset
  branches in handleFileUpload/handleZipUpload
- delete the orphaned confluence-icon.tsx component (no remaining importers)

Markdown, HTML, Notion and the generic zip upload remain unchanged.

apps/client/src/components/icons/confluence-icon.tsx

@@ -1,20 +0,0 @@
-import { rem } from "@mantine/core";
-
-interface Props {
-  size?: number | string;
-}
-
-export function ConfluenceIcon({ size }: Props) {
-  return (
-    <svg
-      xmlns="http://www.w3.org/2000/svg"
-      viewBox="0 0 24 24"
-      fill="none"
-      stroke="currentColor"
-      strokeWidth="2"
-      style={{ width: rem(size), height: rem(size) }}
-    >
-      <path d="M.87 18.257c-.248.382-.53.875-.763 1.245a.764.764 0 0 0 .255 1.04l4.965 3.054a.764.764 0 0 0 1.058-.26c.199-.332.454-.763.733-1.221 1.967-3.247 3.945-2.853 7.508-1.146l4.957 2.337a.764.764 0 0 0 1.028-.382l2.364-5.346a.764.764 0 0 0-.382-1 599.851 599.851 0 0 1-4.965-2.361C10.911 10.97 5.224 11.185.87 18.257zM23.131 5.743c.249-.405.531-.875.764-1.25a.764.764 0 0 0-.256-1.034L18.675.404a.764.764 0 0 0-1.058.26c-.195.335-.451.763-.734 1.225-1.966 3.246-3.945 2.85-7.508 1.146L4.437.694a.764.764 0 0 0-1.027.382L1.046 6.422a.764.764 0 0 0 .382 1c1.039.49 3.105 1.467 4.965 2.361 6.698 3.246 12.392 3.029 16.738-4.04z" />
-    </svg>
-  );
-}