feat: harden support, localize knowledge and add operator availability [skip ci]

Source-only publication of reviewed commit 64e96a7f423673dc29ad56485be9fc79bce8af1c.

Passed in isolation: focused frontend/backend tests, race checks, TypeScript typecheck, lint, Go compilation, Flowgram build, and deterministic SDK build/tests.

Not accepted as a production release: Next.js export/native assembly remains blocked by environment memory limits; browser interaction and MySQL staging acceptance remain unverified. No production server, database/schema, runtime configuration, deployment, release tag, or workflow execution was performed.

Expected source tree: 0a4a7528e9.

internal/services/test_network_test.go

@@ -0,0 +1,78 @@
+package services
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+
+	"agent-desk/internal/models"
+)
+
+// Service integration fixtures may enqueue outbound work asynchronously. Keep
+// those clients inside this test process's loopback fixtures even when a test
+// accidentally supplies an external URL. Production transports are unchanged.
+type loopbackTestTransport struct {
+	base http.RoundTripper
+}
+
+func (t loopbackTestTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	host := req.URL.Hostname()
+	ip := net.ParseIP(host)
+	if host != "localhost" && (ip == nil || !ip.IsLoopback()) {
+		return nil, fmt.Errorf("external HTTP transport disabled in service tests: %s", host)
+	}
+	return t.base.RoundTrip(req)
+}
+
+func TestMain(m *testing.M) {
+	// These service fixtures do not contain AI-runtime tables/configuration.
+	// Runtime behavior has its own suite; focused hook tests install their own
+	// spies. Never let a transitive runtime init launch unowned background work.
+	TriggerAIReplyAsyncHook = func(models.Conversation, models.Message) {}
+	transport := http.DefaultTransport.(*http.Transport).Clone()
+	transport.Proxy = nil
+	http.DefaultTransport = loopbackTestTransport{base: transport}
+	os.Exit(m.Run())
+}
+
+type testRoundTripper func(*http.Request) (*http.Response, error)
+
+func (f testRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	return f(req)
+}
+
+func TestServiceTransportRejectsExternalHostsBeforeDial(t *testing.T) {
+	for _, address := range []string{"https://slack.com/api/chat.postMessage", "https://api.telegram.org/test", "http://example.invalid", "http://192.0.2.1", "http://[2001:db8::1]"} {
+		t.Run(address, func(t *testing.T) {
+			transport := loopbackTestTransport{base: testRoundTripper(func(*http.Request) (*http.Response, error) {
+				t.Fatal("external request reached the underlying transport")
+				return nil, nil
+			})}
+			req, err := http.NewRequest(http.MethodGet, address, nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if _, err := transport.RoundTrip(req); err == nil {
+				t.Fatal("external request was not blocked")
+			}
+		})
+	}
+}
+
+func TestServiceTransportRejectsRedirectOutsideLoopback(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, "https://example.invalid/forbidden", http.StatusFound)
+	}))
+	defer server.Close()
+	response, err := http.Get(server.URL)
+	if response != nil {
+		response.Body.Close()
+	}
+	if err == nil || !strings.Contains(err.Error(), "external HTTP transport disabled") {
+		t.Fatalf("redirect did not hit the loopback guard: %v", err)
+	}
+}