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/package.json

@@ -18,31 +18,32 @@
   },
   "dependencies": {
     "@anthropic-ai/sdk": "^0.72.1",
-    "@mosaic/shared": "workspace:*",
     "@mosaic/config": "workspace:*",
+    "@mosaic/shared": "workspace:*",
+    "@nestjs/bullmq": "^11.0.4",
     "@nestjs/common": "^11.1.12",
+    "@nestjs/config": "^4.0.2",
     "@nestjs/core": "^11.1.12",
     "@nestjs/platform-express": "^11.1.12",
-    "@nestjs/config": "^4.0.2",
-    "@nestjs/bullmq": "^11.0.4",
     "bullmq": "^5.67.2",
-    "ioredis": "^5.9.2",
     "dockerode": "^4.0.2",
-    "simple-git": "^3.27.0",
-    "zod": "^3.24.1",
+    "ioredis": "^5.9.2",
     "reflect-metadata": "^0.2.2",
-    "rxjs": "^7.8.1"
+    "rxjs": "^7.8.1",
+    "simple-git": "^3.27.0",
+    "zod": "^3.24.1"
   },
   "devDependencies": {
     "@nestjs/cli": "^11.0.6",
     "@nestjs/schematics": "^11.0.1",
     "@nestjs/testing": "^11.1.12",
     "@types/dockerode": "^3.3.31",
-    "@types/node": "^22.13.4",
     "@types/express": "^5.0.1",
-    "typescript": "^5.8.2",
-    "vitest": "^4.0.18",
+    "@types/node": "^22.13.4",
+    "@vitest/coverage-v8": "^4.0.18",
     "ts-node": "^10.9.2",
-    "tsconfig-paths": "^4.2.0"
+    "tsconfig-paths": "^4.2.0",
+    "typescript": "^5.8.2",
+    "vitest": "^4.0.18"
   }
 }