fix: use SQLite-compatible space format in utcnow_iso(), fix credits ordering

utcnow_iso() now produces 'YYYY-MM-DD HH:MM:SS' (space separator) matching
SQLite's datetime('now') so lexicographic comparisons like
'published_at <= datetime(now)' work correctly.

Also add `id DESC` tiebreaker to get_ledger() ORDER BY to preserve
insertion order when multiple credits are added within the same second.

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

web/tests/test_content.py

@@ -8,9 +8,7 @@ sitemap integration, admin CRUD routes, and path collision prevention.
 import importlib
 import json
 import sqlite3
-from datetime import date, datetime
-
-from padelnomics.core import utcnow_iso
+from datetime import date
 from pathlib import Path
 
 import pytest
@@ -21,7 +19,7 @@ from padelnomics.content.routes import (
     bake_scenario_cards,
     is_reserved_path,
 )
-from padelnomics.core import execute, fetch_all, fetch_one, slugify
+from padelnomics.core import execute, fetch_all, fetch_one, slugify, utcnow_iso
 from padelnomics.planner.calculator import calc, validate_state
 
 SCHEMA_PATH = Path(__file__).parent.parent / "src" / "padelnomics" / "migrations" / "schema.sql"