Add remark-gfm for markdown table rendering in Knowledge Base

Tables are a GitHub Flavored Markdown extension not supported by
react-markdown's default parser. Added remark-gfm plugin so tables,
strikethrough, and task lists render correctly in KB articles.

frontend/package.json

@@ -15,6 +15,7 @@
     "react-scripts": "5.0.1",
     "recharts": "^3.8.1",
     "rehype-sanitize": "^6.0.0",
+    "remark-gfm": "^3.0.1",
     "web-vitals": "^2.1.4",
     "xlsx": "^0.18.5"
   },
@@ -30,7 +31,16 @@
       "react-app/jest"
     ],
     "rules": {
-      "no-unused-vars": ["warn", { "vars": "all", "args": "after-used", "ignoreRestSiblings": true, "varsIgnorePattern": "^_", "argsIgnorePattern": "^_" }]
+      "no-unused-vars": [
+        "warn",
+        {
+          "vars": "all",
+          "args": "after-used",
+          "ignoreRestSiblings": true,
+          "varsIgnorePattern": "^_",
+          "argsIgnorePattern": "^_"
+        }
+      ]
     }
   },
   "browserslist": {

frontend/src/components/KnowledgeBaseViewer.js

@@ -1,5 +1,6 @@
 import React, { useState, useEffect, useRef } from 'react';
 import ReactMarkdown from 'react-markdown';
+import remarkGfm from 'remark-gfm';
 import rehypeSanitize from 'rehype-sanitize';
 import mermaid from 'mermaid';
 import { X, Download, Loader, AlertCircle, FileText, File } from 'lucide-react';
@@ -234,6 +235,7 @@ export default function KnowledgeBaseViewer({ article, onClose }) {
             {isMarkdown && (
               <div className="markdown-content">
                 <ReactMarkdown
+                  remarkPlugins={[remarkGfm]}
                   rehypePlugins={[rehypeSanitize]}
                   components={{
                     code({ inline, className, children }) {