feat(files-block): icons for tsv/json/xml/py/js/ts/rs/sh

iconForExt now matches the backend's expanded ALLOWED_EXTENSIONS:
- tsv routes to the excel-box icon (alongside csv).
- json → mdi:code-json, xml/html → mdi:xml.
- py → mdi:language-python; js/ts/jsx/tsx → language-javascript;
  rs → language-rust; sh/bash → console.

Visitors who download a CMS-hosted dataset, source dump or archive
now see a meaningful icon instead of the generic file-outline
fallback.

src/lib/components/blocks/FilesBlock.svelte

@@ -38,6 +38,7 @@
       case "xlsx":
       case "ods":
       case "csv":
+      case "tsv":
         return "mdi:file-excel-box";
       case "ppt":
       case "pptx":
@@ -57,6 +58,24 @@
       case "txt":
       case "md":
         return "mdi:file-document-outline";
+      case "json":
+        return "mdi:code-json";
+      case "xml":
+      case "html":
+      case "htm":
+        return "mdi:xml";
+      case "py":
+        return "mdi:language-python";
+      case "js":
+      case "ts":
+      case "tsx":
+      case "jsx":
+        return "mdi:language-javascript";
+      case "rs":
+        return "mdi:language-rust";
+      case "sh":
+      case "bash":
+        return "mdi:console";
       default:
         return "mdi:file-outline";
     }