test: improve health.ts and browser.ts coverage

- health.ts: Added tests for timeout race, version regex edge cases, non-Error catch blocks
- browser.ts: Added comprehensive edge case test for buildPdfOptions with all fields
- Branch coverage: health.ts improved from 50% to 83.33%
- Function coverage: health.ts improved from 75% to 100%
- Overall function coverage improved from 84.46% to 84.95%
- Total tests: 772 → 776 (+4 new tests)

src/__tests__/health.test.ts

@@ -84,4 +84,55 @@ describe("GET /health", () => {
     // Verify client.release(true) was called to destroy the bad connection
     expect(mockRelease).toHaveBeenCalledWith(true);
   });
+
+  it("returns 503 when database health check times out (timeout race wins)", async () => {
+    // Make pool.connect() hang longer than HEALTH_CHECK_TIMEOUT_MS (3000ms)
+    const mockClient = {
+      query: vi.fn(),
+      release: vi.fn(),
+    };
+    
+    vi.mocked(pool.connect).mockImplementation(() => 
+      new Promise((resolve) => {
+        // Resolve after 5000ms, which is longer than the 3000ms timeout
+        setTimeout(() => resolve(mockClient as any), 5000);
+      })
+    );
+
+    const res = await request(app).get("/health");
+
+    expect(res.status).toBe(503);
+    expect(res.body.status).toBe("degraded");
+    expect(res.body.database.status).toBe("error");
+    expect(res.body.database.message).toContain("Database health check timed out");
+  });
+
+  it("returns PostgreSQL for version string without PostgreSQL match", async () => {
+    const mockClient = {
+      query: vi.fn()
+        .mockResolvedValueOnce({ rows: [{ 1: 1 }] }) // SELECT 1
+        .mockResolvedValueOnce({ rows: [{ version: "MySQL 8.0.33" }] }), // No PostgreSQL in version string
+      release: vi.fn(),
+    };
+    vi.mocked(pool.connect).mockResolvedValue(mockClient as any);
+
+    const res = await request(app).get("/health");
+
+    expect(res.status).toBe(200);
+    expect(res.body.status).toBe("ok");
+    expect(res.body.database.status).toBe("ok");
+    expect(res.body.database.version).toBe("PostgreSQL"); // fallback when no regex match
+  });
+
+  it("returns 503 when non-Error is thrown in catch block", async () => {
+    // Make pool.connect() throw a non-Error object
+    vi.mocked(pool.connect).mockRejectedValue("String error message");
+
+    const res = await request(app).get("/health");
+
+    expect(res.status).toBe(503);
+    expect(res.body.status).toBe("degraded");
+    expect(res.body.database.status).toBe("error");
+    expect(res.body.database.message).toBe("Database connection failed");
+  });
 });