refactor: Address PR review feedback (#1570)

1. Move inline DB init script to external file (scripts/ci/init_test_database.py)
   for better maintainability per djpetti's suggestion.

2. Fail fast in CI when pre-created user login fails instead of falling back
   to slow registration. This makes debugging easier - if the CI user doesn't
   work, something is wrong with workflow setup and should be fixed there.
   Per djpetti's suggestion about developer experience.

The external script is now shared between critical-ui-tests.yml and
extended-ui-tests.yml, reducing duplication.

Co-authored-by: Daniel Petti <djpetti@gmail.com>

scripts/ci/init_test_database.py

@@ -0,0 +1,70 @@
+#!/usr/bin/env python3
+"""
+Initialize test database with pre-created test user for CI.
+
+This script creates the test_admin user BEFORE tests run, avoiding the slow
+registration process (2+ min) which:
+1. Creates encrypted SQLCipher database
+2. Derives encryption keys from password
+3. Creates 58 database tables
+4. Imports 500+ settings from JSON files
+
+Usage:
+    python scripts/ci/init_test_database.py
+
+Environment variables:
+    LDR_DATA_DIR: Directory for database files (required for path consistency)
+    TEST_ENV: Should be "true" for test environment
+
+Note: Test user credentials must match CI_TEST_USER in tests/ui_tests/auth_helper.js
+"""
+
+import os
+from pathlib import Path
+
+
+def main():
+    """Create test database and test_admin user."""
+    # Test user credentials - must match CI_TEST_USER in auth_helper.js
+    TEST_USERNAME = "test_admin"
+    TEST_PASSWORD = "testpass123"  # pragma: allowlist secret
+
+    # Use LDR_DATA_DIR if set, otherwise default
+    data_dir = Path(
+        os.environ.get(
+            "LDR_DATA_DIR",
+            Path.home() / ".local" / "share" / "local-deep-research",
+        )
+    )
+    print(f"Using data directory: {data_dir}")
+    data_dir.mkdir(parents=True, exist_ok=True)
+    (data_dir / "encrypted_databases").mkdir(parents=True, exist_ok=True)
+
+    # Import after setting up paths
+    from local_deep_research.database.auth_db import (
+        get_auth_db_session,
+        init_auth_database,
+    )
+    from local_deep_research.database.encrypted_db import db_manager
+    from local_deep_research.database.models.auth import User
+
+    # Initialize auth database
+    init_auth_database()
+
+    # Create test user in auth database (no password stored)
+    session = get_auth_db_session()
+    user = User(username=TEST_USERNAME)
+    session.add(user)
+    session.commit()
+    session.close()
+
+    # Create user's encrypted database with password
+    db_manager.create_user_database(TEST_USERNAME, TEST_PASSWORD)
+
+    print("✅ Database initialized successfully")
+    print(f"✅ Test user '{TEST_USERNAME}' created")
+    print(f"   Encrypted databases in: {data_dir / 'encrypted_databases'}")
+
+
+if __name__ == "__main__":
+    main()