feat(seed): Greenfield full timetable seed with classes and student enrollment

seed_greenfield_timetable.py creates the complete school data set:
- POST /timetable/setup: school_timetables, academic_years, terms, weeks, days
- POST /timetable/materialize-periods: 1624 academic_periods (203 days x 8 periods)
- 17 classes (Physics/Maths/English/History/Science, Yr7-12) with correct metadata
- class_teachers links (primary teacher per class)
- teacher timetable init + slot assignments (class_id FK patched onto slots)
- class_students enrollment: student1->Yr9 (5 classes), student2->Yr10 (4), student3->Yr11 (2)
- POST /timetable/materialize: 1462 taught_lessons all with class_id populated
- POST /admin/seed-timetable endpoint wired in platform_admin_router

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

routers/database/tools/platform_admin_router.py

@@ -146,3 +146,15 @@ async def seed_environment(
     loop = asyncio.get_event_loop()
     result = await loop.run_in_executor(None, _seed)
     return {"status": "ok", **result}
+
+
+@router.post("/seed-timetable")
+async def seed_greenfield_timetable(
+    _: dict = Depends(require_platform_admin),
+) -> Dict[str, Any]:
+    """Seed full timetable + taught lessons for Greenfield Academy. Platform admin only."""
+    import asyncio
+    from run.initialization.seed_greenfield_timetable import seed as _seed
+    loop = asyncio.get_event_loop()
+    result = await loop.run_in_executor(None, _seed)
+    return {"status": "ok", **result}