Add campaign UTM links and piha.li shortener as a core helper.

Keep mint/UTM in always-on core so email_sms and directmail stay optional, and brand utm_source from SITE_NAME (or UTM_SOURCE) instead of a hardcoded client name.
Closes #3

site/directmail/tests.py

@@ -279,3 +279,65 @@ class PostcardDesignPickTests(TestCase):
         self.assertEqual(campaign.messages.count(), 1)
 
 
+class PostcardUtmPanelTests(TestCase):
+    def setUp(self):
+        User = get_user_model()
+        self.user = User.objects.create_user(
+            username="utm-mail", password="test-pass-123"
+        )
+        self.client = Client()
+        self.client.login(username="utm-mail", password="test-pass-123")
+        self.contact = Contact.objects.create(
+            email="mail@example.com",
+            first_name="Pat",
+            postal_address=Contact.make_postal_address(line1="9 Main"),
+        )
+
+    def test_composer_shows_tracked_link_panel(self):
+        with patch(
+            "directmail.views._fetch_pcm_designs",
+            return_value=([], ""),
+        ):
+            url = reverse("directmail:campaign_list")
+            response = self.client.get(url)
+        self.assertEqual(response.status_code, 200)
+        self.assertContains(response, "Tracked site link")
+        self.assertContains(response, "campaign-utm.js")
+        self.assertContains(response, "qrcode.min.js")
+        self.assertContains(response, "data-utm-qr")
+        self.assertContains(response, reverse("campaign_short_link"))
+
+    def test_postcard_does_not_inject_into_body(self):
+        campaign = create_campaign_draft(
+            name="March mailer",
+            audience=Campaign.Audience.POSTCARD_OPT_IN,
+            body="Internal note only",
+            created_by=self.user,
+        )
+        self.assertEqual(campaign.body_override, "Internal note only")
+        self.assertNotIn("utm_source", campaign.body_override)
+
+    @override_settings(
+        PUBLIC_SITE_URL="https://acmehvac.com",
+        SITE_NAME="Acme HVAC",
+        UTM_SOURCE="",
+        SHORTENER_BASE_URL="",
+        SHORTENER_API_TOKEN="",
+    )
+    def test_detail_shows_tracked_url(self):
+        campaign = create_campaign_draft(
+            name="March mailer",
+            audience=Campaign.Audience.POSTCARD_OPT_IN,
+            body="Internal note only",
+            created_by=self.user,
+        )
+        url = reverse("directmail:campaign_detail", kwargs={"pk": campaign.pk})
+        response = self.client.get(url)
+        self.assertEqual(response.status_code, 200)
+        self.assertContains(response, "utm_campaign=march-mailer")
+        self.assertContains(response, "utm_medium=postcard")
+        self.assertContains(response, "qrcode.min.js")
+        self.assertNotContains(response, "Internal note onlyutm")
+
+
+