fix: code review cleanup - schema sync, type safety, null handling

- Sync KnowledgeLink schema with migration (add displayText, positionStart, positionEnd, resolved)
- Make targetId optional to support unresolved links
- Fix null handling in graph.service.ts (skip unresolved links)
- Add explicit types to frontend components (remove implicit any)
- Remove unused WikiLink import
- Add null-safe statusInfo check in EntryCard

apps/api/src/knowledge/services/link-sync.service.ts

@@ -1,7 +1,7 @@
 import { Injectable } from "@nestjs/common";
 import { PrismaService } from "../../prisma/prisma.service";
 import { LinkResolutionService } from "./link-resolution.service";
-import { parseWikiLinks, WikiLink } from "../utils/wiki-link-parser";
+import { parseWikiLinks } from "../utils/wiki-link-parser";
 
 /**
  * Represents a backlink to a knowledge entry