feat(backend): enforce campaign scheduling, add reviewer queue filter, tactic order, duplicate-test counts

- start_execution now blocks a test from starting before its campaign's
  start_date, closing a gap where the field was persisted but never
  enforced
- GET /tests gains a reviewer_id "my reviews" filter for the red_review/
  blue_review lead-gate stage, distinct from pending_validation_side
  (which only ever covered the later in_review stage and ignored
  assignment entirely)
- get_coverage_by_tactic now returns all 14 MITRE tactics in canonical
  kill-chain order instead of an alphabetical, partial list — the
  regular Dashboard and Executive Dashboard both consume this endpoint
  and previously disagreed on order/completeness
- test-template listing now includes existing_test_count per technique
  so the catalog can warn before creating a likely-duplicate test

backend/app/services/test_crud_service.py

@@ -10,6 +10,7 @@ from datetime import datetime
 from typing import Any
 
 # Import Session, joinedload from sqlalchemy.orm
+from sqlalchemy import or_
 from sqlalchemy.orm import Session, joinedload
 
 # Import  from app.domain.errors
@@ -63,6 +64,8 @@ def list_tests(
     created_by: uuid.UUID | None = None,
     # Entry: pending_validation_side
     pending_validation_side: str | None = None,
+    # Entry: reviewer_id — "my reviews" queue for the red_review/blue_review gate stage
+    reviewer_id: uuid.UUID | None = None,
     not_in_any_campaign: bool = False,
     offset: int = 0,
     # Entry: limit
@@ -101,6 +104,23 @@ def list_tests(
             Test.state == TestState.in_review,
             Test.blue_validation_status.in_(["pending", None]),
         )
+    # "My reviews" — tests currently assigned to *reviewer_id* at the
+    # red_review/blue_review lead-review gate (distinct from
+    # pending_validation_side, which covers the later in_review stage).
+    if reviewer_id:
+        if state == TestState.red_review.value:
+            query = query.filter(Test.red_reviewer_assignee == reviewer_id)
+        elif state == TestState.blue_review.value:
+            query = query.filter(Test.blue_reviewer_assignee == reviewer_id)
+        else:
+            query = query.filter(
+                Test.state.in_([TestState.red_review, TestState.blue_review]),
+                or_(
+                    Test.red_reviewer_assignee == reviewer_id,
+                    Test.blue_reviewer_assignee == reviewer_id,
+                ),
+            )
+
     if not_in_any_campaign:
         linked = db.query(CampaignTest.test_id).distinct().subquery()
         query = query.filter(~Test.id.in_(linked))