Add unit test suite with pytest configuration

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

tests/conftest.py

@@ -0,0 +1,11 @@
+import os
+import sys
+
+# Ensure project root is on the path so imports work
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+# Set FERNET_KEY for tests that import email models (EncryptedTextField needs it at import time)
+if "FERNET_KEY" not in os.environ:
+    from cryptography.fernet import Fernet
+
+    os.environ["FERNET_KEY"] = Fernet.generate_key().decode()