i18n: improve translations across horilla (#1014)

- Added trans() / _() translations to models, forms and templates.
- Updated Spanish locale (django.po).
- Fixed missing verbose_name translations.

Known issues:
- "Leave Type" label in horilla/leave/forms.py not translating.
- "Performance" and "Mails automations" still pending.

facedetection/forms.py

@@ -2,10 +2,11 @@ from django.template.loader import render_to_string
 
 from base.forms import ModelForm
 from facedetection.models import FaceDetection
+from django.utils.translation import gettext_lazy as _
 
 
 class FaceDetectionSetupForm(ModelForm):
-    verbose_name = "Facedetection Configuration"
+    verbose_name = _("Facedetection Configuration")
 
     class Meta:
         model = FaceDetection