feat(strommix): variant system + wald palette + UX polish

Add full/compact variants, prominent share, source badge, big
negative-price banner with conditional disclaimer, cards-style
context row, fade-in animation, and remove em-dashes from
visible strings.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/translations.ts

@@ -204,6 +204,9 @@ const TRANSLATION_KEYS = [
   "strommix_conventional_explanation",
   "strommix_stored_data",
   "strommix_how_calculated",
+  // Compact variant for homepage / sidebar.
+  "strommix_compact_label",         // {{pct}}, {{status}}
+  "strommix_compact_more",
 ] as const;
 
 export type TranslationKey = (typeof TRANSLATION_KEYS)[number];