Add Python 3.13 support with uuid7 backport compatibility

- Create uuid_compat.py module that provides uuid7 for Python <3.14
  using uuid_extensions package, and native uuid.uuid7 for Python 3.14+
- Update all model files and migrations to use archivebox.uuid_compat
- Add uuid7 conditional dependency in pyproject.toml for Python <3.14
- Update requires-python to >=3.13 (from >=3.14)
- Update GitHub workflows, lock_pkgs.sh to use Python 3.13
- Update tool configs (ruff, pyright, uv) for Python 3.13

This enables running ArchiveBox on Python 3.13 while maintaining
forward compatibility with Python 3.14's native uuid7 support.

bin/lock_pkgs.sh

@@ -45,7 +45,7 @@ echo
 echo
 
 echo "[+] Generating dev & prod requirements.txt & pdm.lock from pyproject.toml..."
-uv venv --allow-existing --python 3.14
+uv venv --allow-existing --python 3.13
 source .venv/bin/activate
 echo
 echo "pyproject.toml:    archivebox $(grep 'version = ' pyproject.toml | head -n 1 | awk '{print $3}' | jq -r)"