Add missing admin translations for Fixed Price field

Updated all translation files with new strings from v1.1.4:
- Simplified "How to calculate the price" description
- New "Fixed Price" field label
- New "Enter the fixed price for this composable product" description

Translations added to all 6 locales:
- de_DE (German formal): Festpreis / Geben Sie den Festpreis ein
- de_DE_informal (German informal): Festpreis / Gib den Festpreis ein
- de_CH (Swiss German formal): Festpreis / Geben Sie den Festpreis ein
- de_CH_informal (Swiss German informal): Festpreis / Gib den Festpreis ein
- fr_CH (Swiss French): Prix fixe / Entrez le prix fixe
- it_CH (Swiss Italian): Prezzo fisso / Inserisci il prezzo fisso

All admin strings are now fully translated across all supported locales.

Updated CLAUDE.md "Bugs found" section to mark admin translation task as completed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -251,7 +251,7 @@ unzip -l wc-composable-product-vX.X.X.zip
 ## Bugs found
 
 - ✅ ~~There is a bug related to twig in the frontend area. Documented in `logs/fatal-errors*.log`~~ **FIXED in v1.1.5**
-- Translate the admin area, too
+- ✅ ~~Translate the admin area, too~~ **COMPLETED in v1.1.6** - All admin strings now translated to 6 locales
 
 ## Session History