feat(#66): implement tag filtering in search API endpoint

Add support for filtering search results by tags in the main search endpoint.

Changes:
- Add tags parameter to SearchQueryDto (comma-separated tag slugs)
- Implement tag filtering in SearchService.search() method
- Update SQL query to join with knowledge_entry_tags when tags provided
- Entries must have ALL specified tags (AND logic)
- Add tests for tag filtering (2 controller tests, 2 service tests)
- Update endpoint documentation
- Fix non-null assertion linting error

The search endpoint now supports:
- Full-text search with ranking (ts_rank)
- Snippet generation with highlighting (ts_headline)
- Status filtering
- Tag filtering (new)
- Pagination

Example: GET /api/knowledge/search?q=api&tags=documentation,tutorial

All tests pass (25 total), type checking passes, linting passes.

Fixes #66

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/orchestrator/src/api/health/health.controller.ts

@@ -1,13 +1,15 @@
 import { Controller, Get } from "@nestjs/common";
+import { HealthService } from "./health.service";
 
 @Controller("health")
 export class HealthController {
+  constructor(private readonly healthService: HealthService) {}
+
   @Get()
   check() {
     return {
-      status: "ok",
-      service: "orchestrator",
-      version: "0.0.6",
+      status: "healthy",
+      uptime: this.healthService.getUptime(),
       timestamp: new Date().toISOString(),
     };
   }