feat(dev): improve Rocky Linux and RHEL compatibility for local development

- Relax libvirt-python and lxml version pins to allow precompiled distro packages
- Add PEP 508 environment marker to crypt-r (python_version >= 3.13) to avoid unnecessary C compilation on Python 3.12
- Add stdlib crypt fallback when crypt_r is not available in instances/views.py
- Make LDAP imports and configuration optional in settings.py.template
- Add --system-site-packages and missing packages in webvirtcloud.sh for RHEL/CentOS
- Update README with working Rocky Linux / RHEL / Fedora installation and local dev setup

instances/views.py

@@ -1,4 +1,7 @@
-import crypt_r
+try:
+    import crypt_r as crypt
+except ImportError:
+    import crypt
 import json
 import os
 import re
@@ -476,7 +479,7 @@ def set_root_pass(request, pk):
     if request.method == "POST":
         passwd = request.POST.get("passwd", None)
         if passwd:
-            passwd_hash = crypt_r.crypt(passwd, "$6$kgPoiREy")
+            passwd_hash = crypt.crypt(passwd, "$6$kgPoiREy")
             data = {"action": "password", "passwd": passwd_hash, "vname": instance.name}
 
             if instance.proxy.get_status() == 5: