refactor: use datetime.UTC alias instead of timezone.utc

Python 3.11 introduced datetime.UTC as a cleaner alias for
datetime.timezone.utc. Both build.py and fetch_github_stars.py
are updated to use the shorter form.

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

website/build.py

@@ -4,7 +4,7 @@
 import json
 import re
 import shutil
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 from pathlib import Path
 from typing import TypedDict
 
@@ -189,7 +189,7 @@ def build(repo_root: str) -> None:
             total_entries=total_entries,
             total_categories=len(categories),
             repo_stars=repo_stars,
-            build_date=datetime.now(timezone.utc).strftime("%B %d, %Y"),
+            build_date=datetime.now(UTC).strftime("%B %d, %Y"),
             sponsors=sponsors,
         ),
         encoding="utf-8",

website/fetch_github_stars.py

@@ -5,7 +5,7 @@ import json
 import os
 import re
 import sys
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 from pathlib import Path
 
 import httpx
@@ -110,7 +110,7 @@ def main() -> None:
     print(f"Found {len(current_repos)} GitHub repos in README.md")
 
     cache = load_stars(CACHE_FILE)
-    now = datetime.now(timezone.utc)
+    now = datetime.now(UTC)
 
     # Prune entries not in current README
     pruned = {k: v for k, v in cache.items() if k in current_repos}