Update diary view with new buttons

CLAUDE.md

@@ -65,6 +65,11 @@ When building features, apply this order:
 3. Simplicity of implementation, adhere to KISS
 4. Performance
 
+## Date Formatting
+
+- General UI dates (file listings, metadata): ISO `YYYY-MM-DD`
+- Diary long-form dates: German locale, e.g. `Mittwoch, 1. April 2026` — use `formatGermanDate` in `diary.go`; Go's `time.Format` is English-only so locale names are kept in maps keyed by `time.Weekday` / `time.Month`
+
 ## What to Avoid
 
 - Any parallel folder structure (e.g. a separate `media/` tree mirroring `pages/`)