refactor(sidebar): remove pin/unpin and global hide, use per-page hide only

- Remove pin/unpin and auto-hide hover mechanism (isPinned, isHovering,
  hoverTimeout, showSidebar/hideSidebar, updateAutoHideState, etc.)
- Remove global show_folder_sidebar setting (SettingsManager,
  PageControls, recipes, backend default)
- Simplify sidebar visibility to a single per-page toggle:
  · Dedicated chevron-left button in header to hide sidebar
  · Edge indicator (chevron-right) to restore when hidden
  · No dropdown, no hover area, no pin button
- Add _migrateOldSettings() to convert old sidebarPinned and
  show_folder_sidebar states to per-page sidebarDisabled
- Fix sidebar flicker on page load: CSS defaults to off-screen,
  JS explicitly sets .visible or .hidden-by-setting
- Remove obsolete CSS classes: auto-hide, hover-active, collapsed
- Remove i18n keys: pinSidebar, unpinSidebar, moreOptions
- Update test mocks for the new initialize() interface

locales/de.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "Stammverzeichnis",
-        "moreOptions": "Weitere Optionen",
         "collapseAll": "Alle Ordner einklappen",
-        "pinSidebar": "Sidebar anheften",
-        "unpinSidebar": "Sidebar lösen",
         "hideOnThisPage": "Seitenleiste auf dieser Seite ausblenden",
         "showSidebar": "Seitenleiste anzeigen",
         "sidebarHiddenNotification": "Seitenleiste auf der Seite {page} ausgeblendet",

locales/en.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "Root",
-        "moreOptions": "More options",
         "collapseAll": "Collapse All Folders",
-        "pinSidebar": "Pin Sidebar",
-        "unpinSidebar": "Unpin Sidebar",
         "hideOnThisPage": "Hide sidebar on this page",
         "showSidebar": "Show sidebar",
         "sidebarHiddenNotification": "Folder sidebar hidden on {page} page",

locales/es.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "Raíz",
-        "moreOptions": "Más opciones",
         "collapseAll": "Colapsar todas las carpetas",
-        "pinSidebar": "Fijar barra lateral",
-        "unpinSidebar": "Desfijar barra lateral",
         "hideOnThisPage": "Ocultar barra lateral en esta página",
         "showSidebar": "Mostrar barra lateral",
         "sidebarHiddenNotification": "Barra lateral oculta en la página {page}",

locales/fr.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "Racine",
-        "moreOptions": "Plus d'options",
         "collapseAll": "Réduire tous les dossiers",
-        "pinSidebar": "Épingler la barre latérale",
-        "unpinSidebar": "Désépingler la barre latérale",
         "hideOnThisPage": "Masquer la barre latérale sur cette page",
         "showSidebar": "Afficher la barre latérale",
         "sidebarHiddenNotification": "Barre latérale masquée sur la page {page}",

locales/he.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "שורש",
-        "moreOptions": "אפשרויות נוספות",
         "collapseAll": "כווץ את כל התיקיות",
-        "pinSidebar": "נעל סרגל צד",
-        "unpinSidebar": "שחרר סרגל צד",
         "hideOnThisPage": "הסתר סרגל צד בדף זה",
         "showSidebar": "הצג סרגל צד",
         "sidebarHiddenNotification": "סרגל הצד מוסתר בדף {page}",

locales/ja.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "ルート",
-        "moreOptions": "その他のオプション",
         "collapseAll": "すべてのフォルダを折りたたむ",
-        "pinSidebar": "サイドバーを固定",
-        "unpinSidebar": "サイドバーの固定を解除",
         "hideOnThisPage": "このページでサイドバーを非表示",
         "showSidebar": "サイドバーを表示",
         "sidebarHiddenNotification": "{page}ページでサイドバーが非表示になっています",

locales/ko.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "루트",
-        "moreOptions": "더 많은 옵션",
         "collapseAll": "모든 폴더 접기",
-        "pinSidebar": "사이드바 고정",
-        "unpinSidebar": "사이드바 고정 해제",
         "hideOnThisPage": "이 페이지에서 사이드바 숨기기",
         "showSidebar": "사이드바 표시",
         "sidebarHiddenNotification": "{page} 페이지에서 사이드바가 숨겨져 있습니다",

locales/ru.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "Корень",
-        "moreOptions": "Дополнительные параметры",
         "collapseAll": "Свернуть все папки",
-        "pinSidebar": "Закрепить боковую панель",
-        "unpinSidebar": "Открепить боковую панель",
         "hideOnThisPage": "Скрыть боковую панель на этой странице",
         "showSidebar": "Показать боковую панель",
         "sidebarHiddenNotification": "Боковая панель скрыта на странице {page}",

locales/zh-CN.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "根目录",
-        "moreOptions": "更多选项",
         "collapseAll": "折叠所有文件夹",
-        "pinSidebar": "固定侧边栏",
-        "unpinSidebar": "取消固定侧边栏",
         "hideOnThisPage": "隐藏此页面侧边栏",
         "showSidebar": "显示侧边栏",
         "sidebarHiddenNotification": "{page}页面的文件夹侧边栏已隐藏",

locales/zh-TW.json

@@ -956,10 +956,7 @@
     },
     "sidebar": {
         "modelRoot": "根目錄",
-        "moreOptions": "更多選項",
         "collapseAll": "全部摺疊資料夾",
-        "pinSidebar": "固定側邊欄",
-        "unpinSidebar": "取消固定側邊欄",
         "hideOnThisPage": "隱藏此頁面側邊欄",
         "showSidebar": "顯示側邊欄",
         "sidebarHiddenNotification": "{page}頁面的資料夾側邊欄已隱藏",