style: drop redundant comments and apply formatting

Frontend now uses double quotes and semicolons. No behaviour change.

backend/tests/__init__.py

@@ -13,7 +13,7 @@ TEST_DATABASE = "books_test"
 
 def _ensure_test_database() -> None:
     conn = psycopg2.connect(ADMIN_URL)
-    conn.autocommit = True  # CREATE DATABASE cannot run inside a transaction
+    conn.autocommit = True
     try:
         with conn.cursor() as cur:
             cur.execute(
@@ -28,6 +28,5 @@ def _ensure_test_database() -> None:
 
 
 _ensure_test_database()
-# Assigned, never defaulted: tests TRUNCATE tables, so they must not inherit a real DATABASE_URL.
 os.environ["DATABASE_URL"] = ADMIN_URL.rsplit("/", 1)[0] + "/" + TEST_DATABASE
 os.environ["PASSWORD_PEPPER"] = "test-pepper-0123456789abcdef0123456789abcdef"