Add API Q1 CAPA: root cause, corrective action gate, effectiveness verification

Implements tester feedback against API Q1 §5.9.1.2 / §6.4.2:

- Root Cause field + 6M Root Cause Category lookup (Man/Machine/Method/
  Material/Measurement/Environment), separate from Deviation Detail/Category
- "Corrective Action Required?" Yes/No gate on every NCR with a required
  justification
- Corrective action plan with owner + due date; owner is notified by email
- Effectiveness verification (result, notes, server-stamped verifier/date)
  required before an NCR can close when corrective action is required —
  costing returns 409 listing the missing pieces
- Recurring-issue flag with bidirectional NCR-to-NCR links; prior NCRs show
  a warning when later NCRs reference them
- Dashboard metrics: % root cause completed, % CAPA verified effective,
  avg CAPA close time, overdue CAPA count, NCRs by root cause category
- CAPA section in the NCR detail UI, printable PDF, CSV export, and the
  vw_ncr_full Power BI view; admin list manager for root cause categories
- Migrations 0003 (schema + seeded 6M lookup) and 0004 (view refresh);
  demo seed data exercises every metric

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/tests/conftest.py

@@ -28,7 +28,14 @@ from httpx import ASGITransport, AsyncClient  # noqa: E402
 
 from app.database import get_engine, get_session_factory  # noqa: E402
 from app.main import app  # noqa: E402
-from app.models import Base, Department, DeviationCategory, User, UserRole  # noqa: E402
+from app.models import (  # noqa: E402
+    Base,
+    Department,
+    DeviationCategory,
+    RootCauseCategory,
+    User,
+    UserRole,
+)
 
 
 @pytest.fixture(scope="session", autouse=True)
@@ -41,6 +48,8 @@ def _create_schema():
             db.add(Department(name="Machining", is_active=True))
             db.add(Department(name="Inactive Dept", is_active=False))
             db.add(DeviationCategory(name="Dimensional", is_active=True))
+            db.add(RootCauseCategory(name="Method", is_active=True))
+            db.add(RootCauseCategory(name="Retired Cause", is_active=False))
             await db.commit()
 
     asyncio.run(_run())