feat(campaigns): campaign start date — scheduled activation, Jira start_date

DB: migration b047 adds start_date (DateTime nullable) + index to campaigns.

Backend:
- Campaign model: start_date field
- CampaignCreate/Update schemas: accept start_date (ISO string)
- CRUD service: persist + serialize start_date in both serializers
- Activation endpoint: blocks manual activation if start_date is in the future
  (campaign will auto-activate via scheduler)
- Scheduler: new hourly job _run_scheduled_campaign_activation — finds draft
  campaigns with start_date <= now, activates them, creates Jira tickets,
  notifies red_tech team
- Jira: campaign + test tickets now include JIRA_START_DATE_FIELD (configurable,
  default customfield_10015). Campaign uses start_date if set, else created_at.
  Tests inherit campaign start_date.
- config.py: JIRA_START_DATE_FIELD setting

Frontend:
- Campaign type: start_date field on Campaign + CampaignSummary
- CampaignCreatePayload: start_date optional field
- Create form: date picker with min=today, warning message explaining behavior
- Campaign detail header: start_date badge showing days remaining or started date

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/services/jira_service.py

@@ -407,6 +407,11 @@ def auto_create_campaign_issue(
             "customfield_10011": campaign.name,
         }
 
+        # Set start date: use campaign.start_date if set, otherwise today
+        effective_start = campaign.start_date or campaign.created_at
+        if effective_start:
+            fields[settings.JIRA_START_DATE_FIELD] = effective_start.strftime("%Y-%m-%d")
+
         # Nest under the configured parent ticket (Initiative, e.g. OFS-20795)
         if parent_ticket:
             fields["parent"] = {"key": parent_ticket}
@@ -446,6 +451,7 @@ def auto_create_test_issue(
     *,
     technique: Optional[Technique] = None,
     parent_ticket_override: Optional[str] = None,
+    campaign_start_date=None,  # datetime | None — inherited from campaign when available
 ) -> Optional[str]:
     """Create a Jira issue for *test* and store the link.
 
@@ -496,6 +502,12 @@ def auto_create_test_issue(
             "customfield_10309": f"{{code}}{poc}{{code}}",
         }
 
+        # Inherit campaign start date if available, otherwise use today
+        from datetime import date as _date
+        effective_start = campaign_start_date or _date.today()
+        if hasattr(effective_start, "strftime"):
+            fields[settings.JIRA_START_DATE_FIELD] = effective_start.strftime("%Y-%m-%d")
+
         if parent:
             fields["parent"] = {"key": parent}