feat: add backlinks display and wiki-link rendering (closes #62, #64)

Implements two key knowledge module features:

**#62 - Backlinks Display:**
- Added BacklinksList component to show entries that link to current entry
- Fetches backlinks from /api/knowledge/entries/:slug/backlinks
- Displays entry title, summary, and link context
- Clickable links to navigate to linking entries
- Loading, error, and empty states

**#64 - Wiki-Link Rendering:**
- Added WikiLinkRenderer component to parse and render wiki-links
- Supports [[slug]] and [[slug|display text]] syntax
- Converts wiki-links to clickable navigation links
- Distinct styling (blue color, dotted underline)
- XSS protection via HTML escaping
- Memoized HTML processing for performance

**Components:**
- BacklinksList.tsx - Backlinks display with empty/loading/error states
- WikiLinkRenderer.tsx - Wiki-link parser and renderer
- Updated EntryViewer.tsx to use WikiLinkRenderer
- Integrated BacklinksList into entry detail page

**API:**
- Added fetchBacklinks() function in knowledge.ts
- Added KnowledgeBacklink type to shared types

**Tests:**
- Comprehensive tests for BacklinksList (8 tests)
- Comprehensive tests for WikiLinkRenderer (14 tests)
- All tests passing with Vitest

**Type Safety:**
- Strict TypeScript compliance
- No 'any' types
- Proper error handling

apps/web/src/app/(authenticated)/knowledge/[slug]/page.tsx

@@ -8,7 +8,14 @@ import { EntryViewer } from "@/components/knowledge/EntryViewer";
 import { EntryEditor } from "@/components/knowledge/EntryEditor";
 import { EntryMetadata } from "@/components/knowledge/EntryMetadata";
 import { VersionHistory } from "@/components/knowledge/VersionHistory";
-import { fetchEntry, updateEntry, deleteEntry, fetchTags } from "@/lib/api/knowledge";
+import { BacklinksList } from "@/components/knowledge/BacklinksList";
+import {
+  fetchEntry,
+  updateEntry,
+  deleteEntry,
+  fetchTags,
+  fetchBacklinks,
+} from "@/lib/api/knowledge";
 
 /**
  * Knowledge Entry Detail/Editor Page
@@ -25,6 +32,11 @@ export default function EntryPage() {
   const [isSaving, setIsSaving] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
+  // Backlinks state
+  const [backlinks, setBacklinks] = useState<any[]>([]);
+  const [backlinksLoading, setBacklinksLoading] = useState(false);
+  const [backlinksError, setBacklinksError] = useState<string | null>(null);
+
   // Edit state
   const [editTitle, setEditTitle] = useState("");
   const [editContent, setEditContent] = useState("");
@@ -56,6 +68,25 @@ export default function EntryPage() {
     void loadEntry();
   }, [slug]);
 
+  // Load backlinks
+  useEffect(() => {
+    async function loadBacklinks(): Promise<void> {
+      try {
+        setBacklinksLoading(true);
+        setBacklinksError(null);
+        const data = await fetchBacklinks(slug);
+        setBacklinks(data.backlinks);
+      } catch (err) {
+        setBacklinksError(
+          err instanceof Error ? err.message : "Failed to load backlinks"
+        );
+      } finally {
+        setBacklinksLoading(false);
+      }
+    }
+    void loadBacklinks();
+  }, [slug]);
+
   // Load available tags
   useEffect(() => {
     async function loadTags(): Promise<void> {
@@ -324,7 +355,18 @@ export default function EntryPage() {
         {isEditing ? (
           <EntryEditor content={editContent} onChange={setEditContent} />
         ) : activeTab === "content" ? (
-          <EntryViewer entry={entry} />
+          <>
+            <EntryViewer entry={entry} />
+            
+            {/* Backlinks Section */}
+            <div className="mt-8 pt-6 border-t border-gray-200 dark:border-gray-700">
+              <BacklinksList
+                backlinks={backlinks}
+                isLoading={backlinksLoading}
+                error={backlinksError}
+              />
+            </div>
+          </>
         ) : (
           <VersionHistory slug={slug} onRestore={handleVersionRestore} />
         )}