Round out referee amounts/colors, and add bilingual (nl/en) news content

Referee display: drop the redundant "External" pill from the PDF form, round
the event/dashboard "due" summary to 2 decimals (a fine-grained km rate like
0.083 was pushing the raw total to 3+ decimals), and theme the PDF's accent
colors off the club's own primary/secondary colors instead of a hardcoded
default.

News: title/body stay the club's own-language (Dutch) text; new optional
title_en/body_en carry a translation, with News.effective_title_en/
effective_body_en resolving the fallback to the original on read rather than
copying it in at save time -- so editing the Dutch text later never leaves a
stale English copy behind, and existing rows get correct fallback behaviour
with no backfill. The news form lays both languages out side by side; the
detail page only shows an English section when one was actually added. The
public API returns both languages in one call (title_nl/body_nl/excerpt_nl
alongside title_en/body_en/excerpt_en, the latter never blank) -- a breaking
rename of the previously-unprefixed title/body/excerpt fields.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

management/forms.py

@@ -522,10 +522,11 @@ class NewsForm(forms.ModelForm):
 
     class Meta:
         model = News
-        fields = ["title", "teams", "visibility", "body"]
+        fields = ["title", "title_en", "teams", "visibility", "body", "body_en"]
         widgets = {
             "teams": forms.SelectMultiple(attrs={"data-searchable": "true", "data-search-placeholder": _("Type to filter teams...")}),
             "body": forms.Textarea(attrs={"rows": 8}),
+            "body_en": forms.Textarea(attrs={"rows": 8}),
         }
 
     def __init__(self, *args, club=None, **kwargs):