Add DE/EN language toggle with bilingual descriptions

- Language switcher in sidebar (DE/EN buttons, persists to localStorage)
- i18n module with pick_desc/pick_name helpers for language-aware fallback
- All detail/list pages use language context for names and descriptions
- Species/Cultivar types updated with description_de/description_en
- Common Name column added to species/families lists

herbapi-ui/src/pages/cultivars.rs

@@ -3,8 +3,9 @@ use std::collections::HashMap;
 use uuid::Uuid;
 
 use crate::api;
-use crate::app::Route;
+use crate::app::{Lang, Route};
 use crate::components::table_controls::*;
+use crate::i18n::{pick_desc, pick_name};
 
 /// Convert a month-number array (1=Jan..12=Dec) to a comma-separated string of abbreviations.
 fn months_display(months: &Option<Vec<i32>>) -> String {
@@ -279,6 +280,7 @@ pub fn CultivarList() -> Element {
 
 #[component]
 pub fn CultivarDetail(slug: String) -> Element {
+    let lang = use_context::<Lang>().0;
     let slug_clone = slug.clone();
     let cultivar = use_resource(move || {
         let s = slug_clone.clone();
@@ -326,11 +328,14 @@ pub fn CultivarDetail(slug: String) -> Element {
                 None => rsx! { p { "Loading..." } },
                 Some(Err(e)) => rsx! { p { class: "error", "Error: {e}" } },
                 Some(Ok(c)) => {
+                    let current_lang = lang.read().clone();
+
                     // Pre-compute display strings outside of rsx
+                    let common_name = pick_name(&current_lang, &c.name_de, &c.name_en, &c.name);
                     let name_en = opt_str(&c.name_en);
                     let name_de = opt_str(&c.name_de);
                     let name_sci = opt_str(&c.name_scientific);
-                    let desc = opt_str(&c.description);
+                    let desc = pick_desc(&current_lang, &c.description_de, &c.description_en, &c.description);
                     let organic = bool_display(c.is_organic);
                     let perennial = bool_display(c.perennial);
 
@@ -369,6 +374,9 @@ pub fn CultivarDetail(slug: String) -> Element {
 
                     rsx! {
                         h1 { "{c.name}" }
+                        if common_name != c.name {
+                            p { class: "name-common", "{common_name}" }
+                        }
 
                         div { class: "detail-row",
                             // === LEFT COLUMN ===
@@ -383,6 +391,10 @@ pub fn CultivarDetail(slug: String) -> Element {
                                                 th { "Name" }
                                                 td { "{c.name}" }
                                             }
+                                            tr {
+                                                th { "Common Name" }
+                                                td { "{common_name}" }
+                                            }
                                             tr {
                                                 th { "Name EN" }
                                                 td { class: if name_en == "\u{2014}" { "placeholder" } else { "" }, "{name_en}" }