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>

auth_db.py

@@ -8,11 +8,15 @@ HRT-79: migration Telegram columns
 import sqlite3
 import os
 
+# NOTE: DB_PATH kept for backward compat, but get_db() reads env at call time
+# so test isolation works correctly when TURF_SAAS_DB is set per-module.
 DB_PATH = os.environ.get("TURF_SAAS_DB", "/home/h3r7/turf_saas/turf_saas.db")
 
 
 def get_db():
-    conn = sqlite3.connect(DB_PATH)
+    # Read env dynamically so test overrides of TURF_SAAS_DB are respected
+    db_path = os.environ.get("TURF_SAAS_DB", DB_PATH)
+    conn = sqlite3.connect(db_path)
     conn.row_factory = sqlite3.Row
     return conn