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.spec.ts

@@ -0,0 +1,99 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import { HealthController } from "./health.controller";
+import { HealthService } from "./health.service";
+
+describe("HealthController", () => {
+  let controller: HealthController;
+  let service: HealthService;
+
+  beforeEach(() => {
+    service = new HealthService();
+    controller = new HealthController(service);
+  });
+
+  describe("GET /health", () => {
+    it("should return 200 OK with correct format", () => {
+      const result = controller.check();
+
+      expect(result).toBeDefined();
+      expect(result).toHaveProperty("status");
+      expect(result).toHaveProperty("uptime");
+      expect(result).toHaveProperty("timestamp");
+    });
+
+    it('should return status as "healthy"', () => {
+      const result = controller.check();
+
+      expect(result.status).toBe("healthy");
+    });
+
+    it("should return uptime as a positive number", () => {
+      const result = controller.check();
+
+      expect(typeof result.uptime).toBe("number");
+      expect(result.uptime).toBeGreaterThanOrEqual(0);
+    });
+
+    it("should return timestamp as valid ISO 8601 string", () => {
+      const result = controller.check();
+
+      expect(typeof result.timestamp).toBe("string");
+      expect(() => new Date(result.timestamp)).not.toThrow();
+
+      // Verify it's a valid ISO 8601 format
+      const date = new Date(result.timestamp);
+      expect(date.toISOString()).toBe(result.timestamp);
+    });
+
+    it("should return only required fields (status, uptime, timestamp)", () => {
+      const result = controller.check();
+
+      const keys = Object.keys(result);
+      expect(keys).toHaveLength(3);
+      expect(keys).toContain("status");
+      expect(keys).toContain("uptime");
+      expect(keys).toContain("timestamp");
+    });
+
+    it("should increment uptime over time", async () => {
+      const result1 = controller.check();
+      const uptime1 = result1.uptime;
+
+      // Wait 1100ms to ensure at least 1 second has passed
+      await new Promise((resolve) => setTimeout(resolve, 1100));
+
+      const result2 = controller.check();
+      const uptime2 = result2.uptime;
+
+      // Uptime should be at least 1 second higher
+      expect(uptime2).toBeGreaterThanOrEqual(uptime1 + 1);
+    });
+
+    it("should return current timestamp", () => {
+      const before = Date.now();
+      const result = controller.check();
+      const after = Date.now();
+
+      const resultTime = new Date(result.timestamp).getTime();
+
+      // Timestamp should be between before and after (within test execution time)
+      expect(resultTime).toBeGreaterThanOrEqual(before);
+      expect(resultTime).toBeLessThanOrEqual(after);
+    });
+  });
+
+  describe("GET /health/ready", () => {
+    it("should return ready status", () => {
+      const result = controller.ready();
+
+      expect(result).toBeDefined();
+      expect(result).toHaveProperty("ready");
+    });
+
+    it("should return ready as true", () => {
+      const result = controller.ready();
+
+      expect(result.ready).toBe(true);
+    });
+  });
+});