Add campaign UTM links and piha.li shortener (#4)

## Summary
- Port Monica campaign UTM + piha.li minting into always-on `core` (`shortener.py`, `campaign_utm.py`) so `email_sms` and `directmail` stay optional and never import each other.
- `utm_source` is a slug of `SITE_NAME` (override with `UTM_SOURCE`). Email gets an HTML `data-campaign-utm` link; SMS gets a plain URL; postcard QR only — no body inject.
- Live composer mints through login+CSRF `POST /portal/campaigns/short-link/` (registered only when an outreach app is installed). Empty `SHORTENER_*` falls back to the long UTM URL.

Reference: [monica_site PR #10](ai_ml_operations/monica_site#10)

Closes #3

## Test plan
- [x] `cd site && uv run python manage.py test` (125 tests)
- [ ] Email composer: type a name, confirm HTML link + `utm_campaign` updates, save draft
- [ ] SMS composer: plain `piha.li` (or long UTM if shortener unset) in the body
- [ ] Postcard composer: QR copies the tracked URL; campaign body has no `utm_source`
- [ ] Campaign report pages show the same panel
- [ ] With `FEATURE_EMAIL_SMS` and `FEATURE_DIRECT_MAIL` off, no extra nav and no `/portal/campaigns/short-link/` route

Reviewed-on: #4

site/email_sms/views.py

@@ -17,10 +17,12 @@ from django.views.decorators.http import require_GET, require_http_methods, requ
 
 from contacts.consent import opted_in_contacts, record_sms_stop
 from contacts.models import Channel
+from core.campaign_utm import ensure_campaign_utm_link, utm_panel_context
 from core.models import StoredFile
 from core.scheduling import parse_scheduled_for
 from email_sms.models import Campaign, Message, ProviderEvent
 from email_sms.services import (
+    channel_for_audience,
     create_campaign_draft,
     enqueue_campaign_send,
     message_is_removable,
@@ -291,6 +293,16 @@ def campaign_list(request):
             form_errors.append("Campaign name is required.")
         if audience not in Campaign.Audience.values:
             form_errors.append("Choose a recipient list.")
+        else:
+            channel = channel_for_audience(audience)
+            if channel in (Channel.EMAIL, Channel.SMS):
+                body = ensure_campaign_utm_link(
+                    body,
+                    name=name or "campaign",
+                    medium=channel,
+                    html=(channel == Channel.EMAIL),
+                )
+                form_data["body"] = body
         if not body:
             form_errors.append("Body is required.")
         if audience == Campaign.Audience.EMAIL_OPT_IN and not subject:
@@ -330,6 +342,7 @@ def campaign_list(request):
             "form_data": form_data,
             "form_errors": form_errors,
             "image_upload_url": reverse("email_sms:campaign_image_upload"),
+            **utm_panel_context(live=True),
         },
     )
 
@@ -353,6 +366,7 @@ def campaign_detail(request, pk):
             "recent_events": ctx["recent_events"],
             "events_title": ctx["events_title"],
             "events_empty": ctx["events_empty"],
+            **utm_panel_context(campaign=campaign, live=False),
             "can_send": campaign.status
             in {
                 Campaign.Status.DRAFT,