refactor(ui): unify search bar placeholder to i18n key header.search.placeholder

- Replace page-specific header.search.placeholders.* keys with a single
  header.search.placeholder key (value: "Search", no ellipsis)
- Keep header.search.notAvailable for the statistics page
- Remove unused placeholder/placeholders/notAvailable entries from all
  10 locale files; preserve options and searchIn keys
- Update Jinja template and JS header to use the new unified key

locales/de.json

@@ -202,13 +202,7 @@
             "statistics": "Statistiken"
         },
         "search": {
-            "placeholder": "Suchen...",
-            "placeholders": {
-                "loras": "LoRAs suchen...",
-                "recipes": "Rezepte suchen...",
-                "checkpoints": "Checkpoints suchen...",
-                "embeddings": "Embeddings suchen..."
-            },
+            "placeholder": "Suchen",
             "options": "Suchoptionen",
             "searchIn": "Suchen in:",
             "notAvailable": "Suche auf Statistikseite nicht verfügbar",

locales/en.json

@@ -202,13 +202,7 @@
             "statistics": "Stats"
         },
         "search": {
-            "placeholder": "Search...",
-            "placeholders": {
-                "loras": "Search LoRAs...",
-                "recipes": "Search recipes...",
-                "checkpoints": "Search checkpoints...",
-                "embeddings": "Search embeddings..."
-            },
+            "placeholder": "Search",
             "options": "Search Options",
             "searchIn": "Search In:",
             "notAvailable": "Search not available on statistics page",

locales/es.json

@@ -202,13 +202,7 @@
             "statistics": "Estadísticas"
         },
         "search": {
-            "placeholder": "Buscar...",
-            "placeholders": {
-                "loras": "Buscar LoRAs...",
-                "recipes": "Buscar recetas...",
-                "checkpoints": "Buscar checkpoints...",
-                "embeddings": "Buscar embeddings..."
-            },
+            "placeholder": "Buscar",
             "options": "Opciones de búsqueda",
             "searchIn": "Buscar en:",
             "notAvailable": "Búsqueda no disponible en la página de estadísticas",

locales/fr.json

@@ -202,13 +202,7 @@
             "statistics": "Statistiques"
         },
         "search": {
-            "placeholder": "Rechercher...",
-            "placeholders": {
-                "loras": "Rechercher des LoRAs...",
-                "recipes": "Rechercher des recipes...",
-                "checkpoints": "Rechercher des checkpoints...",
-                "embeddings": "Rechercher des embeddings..."
-            },
+            "placeholder": "Rechercher",
             "options": "Options de recherche",
             "searchIn": "Rechercher dans :",
             "notAvailable": "Recherche non disponible sur la page de statistiques",

locales/he.json

@@ -202,13 +202,7 @@
             "statistics": "סטטיסטיקה"
         },
         "search": {
-            "placeholder": "חפש...",
-            "placeholders": {
-                "loras": "חפש LoRAs...",
-                "recipes": "חפש מתכונים...",
-                "checkpoints": "חפש checkpoints...",
-                "embeddings": "חפש embeddings..."
-            },
+            "placeholder": "חיפוש",
             "options": "אפשרויות חיפוש",
             "searchIn": "חפש ב:",
             "notAvailable": "חיפוש לא זמין בדף הסטטיסטיקה",

locales/ja.json

@@ -202,13 +202,7 @@
             "statistics": "統計"
         },
         "search": {
-            "placeholder": "検索...",
-            "placeholders": {
-                "loras": "LoRAを検索...",
-                "recipes": "レシピを検索...",
-                "checkpoints": "checkpointを検索...",
-                "embeddings": "embeddingを検索..."
-            },
+            "placeholder": "検索",
             "options": "検索オプション",
             "searchIn": "検索対象：",
             "notAvailable": "統計ページでは検索は利用できません",

locales/ko.json

@@ -202,13 +202,7 @@
             "statistics": "통계"
         },
         "search": {
-            "placeholder": "검색...",
-            "placeholders": {
-                "loras": "LoRA 검색...",
-                "recipes": "레시피 검색...",
-                "checkpoints": "Checkpoint 검색...",
-                "embeddings": "Embedding 검색..."
-            },
+            "placeholder": "검색",
             "options": "검색 옵션",
             "searchIn": "검색 범위:",
             "notAvailable": "통계 페이지에서는 검색을 사용할 수 없습니다",

locales/ru.json

@@ -202,13 +202,7 @@
             "statistics": "Статистика"
         },
         "search": {
-            "placeholder": "Поиск...",
-            "placeholders": {
-                "loras": "Поиск LoRAs...",
-                "recipes": "Поиск рецептов...",
-                "checkpoints": "Поиск checkpoints...",
-                "embeddings": "Поиск embeddings..."
-            },
+            "placeholder": "Поиск",
             "options": "Опции поиска",
             "searchIn": "Искать в:",
             "notAvailable": "Поиск недоступен на странице статистики",

locales/zh-CN.json

@@ -202,13 +202,7 @@
             "statistics": "统计"
         },
         "search": {
-            "placeholder": "搜索...",
-            "placeholders": {
-                "loras": "搜索 LoRA...",
-                "recipes": "搜索配方...",
-                "checkpoints": "搜索 Checkpoint...",
-                "embeddings": "搜索 Embedding..."
-            },
+            "placeholder": "搜索",
             "options": "搜索选项",
             "searchIn": "搜索范围：",
             "notAvailable": "统计页面不可用搜索",

locales/zh-TW.json

@@ -202,13 +202,7 @@
             "statistics": "統計"
         },
         "search": {
-            "placeholder": "搜尋...",
-            "placeholders": {
-                "loras": "搜尋 LoRA...",
-                "recipes": "搜尋配方...",
-                "checkpoints": "搜尋 checkpoint...",
-                "embeddings": "搜尋 embedding..."
-            },
+            "placeholder": "搜尋",
             "options": "搜尋選項",
             "searchIn": "搜尋範圍：",
             "notAvailable": "統計頁面無法搜尋",