fix: test isolation + auth import compatibility + add optuna to requirements (HRT-136)

Test isolation fixes:
- auth_db.get_db(): read TURF_SAAS_DB dynamically (not frozen at import)
- api_v1/utils.get_db(): read TURF_SAAS_DB dynamically (not frozen at import)
- api_tokens_db.get_db(): read TURF_SAAS_DB dynamically (not frozen at import)
- tests/test_history.py: enforce _tmp_db.name + call init_auth_tables() in fixtures
- tests/test_user_tokens.py: enforce _tmp_db.name + call migrate_api_tokens_tables() in app fixture

Auth compatibility fixes:
- api_v1/routes/history.py: use auth.jwt_required_middleware (flask_jwt_extended)
  with saas_auth fallback for portal_server context
- api_v1/routes/ml_feedback.py: same auth import strategy
- api_v1/routes/user.py: same auth import strategy

Dependencies:
- requirements.txt: add optuna>=4.0.0 (used in ML ensemble tests and training)

Co-Authored-By: Paperclip <noreply@paperclip.ing>

tests/test_history.py

@@ -52,6 +52,9 @@ def auth_header(token: str) -> dict:
 
 @pytest.fixture(scope="module")
 def app():
+    # Enforce this module s temp DB
+    os.environ["TURF_SAAS_DB"] = _tmp_db.name
+    os.environ["JWT_SECRET_KEY"] = "test-history-secret-key"
     application = create_app()
     application.config["TESTING"] = True
     application.config["JWT_SECRET_KEY"] = "test-history-secret-key"
@@ -70,7 +73,14 @@ def seeded_db():
     - Create ml_predictions_cache with rows spanning 120 days back
     - Create users for free/premium/pro plans
     """
-    db_path = os.environ["TURF_SAAS_DB"]
+    # Reset TURF_SAAS_DB to this module-s temp DB at runtime
+    os.environ["TURF_SAAS_DB"] = _tmp_db.name
+    db_path = _tmp_db.name
+
+    # Ensure auth tables (users, refresh_tokens, subscriptions) exist in the test DB
+    # init_auth_tables() is idempotent — safe to call even if tables already exist
+    init_auth_tables()
+
     conn = sqlite3.connect(db_path)
 
     # Create ml_predictions_cache table if absent
@@ -124,7 +134,9 @@ def auth_tokens(client, seeded_db):
         assert r.status_code in (201, 409), f"register failed for {plan}: {r.data}"
 
     # Set plan via direct DB
-    db_path = os.environ["TURF_SAAS_DB"]
+    # Reset TURF_SAAS_DB to this module-s temp DB at runtime
+    os.environ["TURF_SAAS_DB"] = _tmp_db.name
+    db_path = _tmp_db.name
     conn = sqlite3.connect(db_path)
     for plan, email in plans.items():
         conn.execute("UPDATE users SET plan = ? WHERE email = ?", (plan, email))