fix: convert CSV validation tests from pytest to Django unittest

The CI runs `python manage.py test` (Django's unittest runner), which
does not have pytest installed. Rewrites the test infrastructure to use
Django's SimpleTestCase and standard unittest patterns:

- Rename conftest.py to csv_data.py (conftest is a pytest convention)
- Replace pytest fixtures with module-level cached data
- Replace pytest parametrize with subTest loops
- Use django.test.SimpleTestCase (no DB access needed)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: DJ-Meyers

tests/csv_validation/conftest.py

@@ -0,0 +1,49 @@
+"""
+CSV data loading helpers for encounter validation tests.
+
+Design for CI/CD efficiency:
+- Module-level caching loads CSVs once per import
+- In-memory validation only (no DB/API calls)
+"""
+
+import csv
+from pathlib import Path
+from typing import Any
+
+from .game_config import GAME_CONFIGS
+
+CSV_DIR = Path(__file__).parent.parent.parent / "data" / "v2" / "csv"
+
+
+def load_csv(filename: str) -> list[dict[str, Any]]:
+    filepath = CSV_DIR / filename
+    if not filepath.exists():
+        raise FileNotFoundError(f"CSV file not found: {filepath}")
+    with open(filepath, "r", encoding="utf-8") as f:
+        return list(csv.DictReader(f))
+
+
+def get_encounters_for_version_group(
+    encounters: list[dict],
+    slots: dict[str, dict],
+    version_group_id: int,
+) -> list[dict]:
+    valid_slot_ids = {
+        slot_id
+        for slot_id, slot in slots.items()
+        if slot.get("version_group_id") == str(version_group_id)
+    }
+    return [enc for enc in encounters if enc.get("encounter_slot_id") in valid_slot_ids]
+
+
+# Module-level cached data (loaded once on import)
+encounters_data = load_csv("encounters.csv")
+encounter_slots_data = load_csv("encounter_slots.csv")
+encounter_methods_data = load_csv("encounter_methods.csv")
+location_areas_data = load_csv("location_areas.csv")
+
+encounter_methods_lookup = {row["id"]: row for row in encounter_methods_data}
+encounter_slots_lookup = {row["id"]: row for row in encounter_slots_data}
+location_areas_lookup = {row["id"]: row for row in location_areas_data}
+
+game_configs = list(GAME_CONFIGS.values())