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>

package.json

@@ -10,6 +10,9 @@
   "scripts": {
     "build": "turbo run build",
     "dev": "turbo run dev",
+    "dev:api": "turbo run dev --filter @mosaic/api",
+    "dev:web": "turbo run dev --filter @mosaic/web",
+    "dev:orchestrator": "turbo run dev --filter @mosaic/orchestrator",
     "lint": "turbo run lint",
     "lint:fix": "turbo run lint:fix",
     "format": "prettier --write \"**/*.{ts,tsx,js,jsx,json,md}\"",
@@ -24,6 +27,10 @@
     "docker:up": "docker compose up -d",
     "docker:down": "docker compose down",
     "docker:logs": "docker compose logs -f",
+    "docker:logs:api": "docker compose logs -f api",
+    "docker:logs:web": "docker compose logs -f web",
+    "docker:logs:orchestrator": "docker compose logs -f orchestrator",
+    "docker:logs:coordinator": "docker compose logs -f coordinator",
     "docker:ps": "docker compose ps",
     "docker:build": "docker compose build",
     "docker:restart": "docker compose restart",