feat(knowledge): add markdown rendering (KNOW-004)

- Install marked, marked-highlight, marked-gfm-heading-id, sanitize-html
- Create markdown utility with GFM support (tables, task lists, strikethrough)
- Add code syntax highlighting with highlight.js
- Implement XSS sanitization for security
- Update knowledge service to use markdown renderer
- Add comprehensive test suite (34 tests, all passing)
- Generate IDs for headers for deep linking
- Cache rendered HTML in database for performance

apps/api/src/knowledge/knowledge.service.ts

@@ -4,7 +4,6 @@ import {
   ConflictException,
 } from "@nestjs/common";
 import { EntryStatus } from "@prisma/client";
-import { marked } from "marked";
 import slugify from "slugify";
 import { PrismaService } from "../prisma/prisma.service";
 import type { CreateEntryDto, UpdateEntryDto, EntryQueryDto } from "./dto";
@@ -12,20 +11,15 @@ import type {
   KnowledgeEntryWithTags,
   PaginatedEntries,
 } from "./entities/knowledge-entry.entity";
+import { renderMarkdown } from "./utils/markdown";
 
 /**
  * Service for managing knowledge entries
  */
 @Injectable()
 export class KnowledgeService {
-  constructor(private readonly prisma: PrismaService) {
-    // Configure marked for security and consistency
-    marked.setOptions({
-      gfm: true, // GitHub Flavored Markdown
-      breaks: false,
-      pedantic: false,
-    });
-  }
+  constructor(private readonly prisma: PrismaService) {}
+
 
   /**
    * Get all entries for a workspace (paginated and filterable)
@@ -175,8 +169,8 @@ export class KnowledgeService {
     const baseSlug = this.generateSlug(createDto.title);
     const slug = await this.ensureUniqueSlug(workspaceId, baseSlug);
 
-    // Render markdown to HTML
-    const contentHtml = await marked.parse(createDto.content);
+    // Render markdown to HTML with sanitization
+    const contentHtml = await renderMarkdown(createDto.content);
 
     // Use transaction to ensure atomicity
     const result = await this.prisma.$transaction(async (tx) => {
@@ -299,7 +293,7 @@ export class KnowledgeService {
     // Render markdown if content is updated
     let contentHtml = existing.contentHtml;
     if (updateDto.content) {
-      contentHtml = await marked.parse(updateDto.content);
+      contentHtml = await renderMarkdown(updateDto.content);
     }
 
     // Build update data object conditionally