Right sidebar nav: Library / Reports / Documentation tabs (WebView2)

The body of the launcher is now a 2-column layout:
- Left : swappable content area
- Right (200px) : sidebar with 3 nav buttons + active-state highlighting

Three pages, all under the same window chrome / footer:

1. **Library** (default) — the existing main view (featured version,
   other versions list, floating "Vérifier les MAJ" button, copyright).
2. **Reports** — embedded WebView2 navigated to a configurable URL.
   Default http://localhost/ProserveReport/ which matches the local
   stats tool installed on each customer machine alongside XAMPP.
3. **Documentation** — WebView2 with a configurable URL, falls back
   to a placeholder explaining where to set it if empty.

Implementation
- LocalConfig gains ReportUrl + DocumentationUrl (string).
- MainViewModel gains LauncherPage enum + CurrentPage state with
  Navigate{Library,Report,Documentation}Command. ReportUri /
  DocumentationUri parse the strings to Uri for WebView2.Source.
- Theme.xaml: NavButton style (transparent, left-aligned, hover
  darken, active state highlighted via Tag bool + accent left-border).
- InverseBoolToVisibilityConverter added (true → Collapsed) for the
  documentation placeholder fallback.
- Microsoft.Web.WebView2 NuGet (1.0.2792.45). Runtime is pre-installed
  on Win11 and auto-pushed via Windows Update on Win10. If absent,
  WebView2 surfaces an error which the user sees inline.
- Settings → Avancés → Serveur extended with the two URL fields.
- Strings.cs: NavLibrary / NavReport / NavDocumentation,
  SettingsReportUrl / SettingsDocsUrl, DocsPlaceholder, WebViewLoadError.
  Sidebar localized in 5 languages.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/PSLauncher.Core/Localization/Strings.cs

@@ -152,6 +152,28 @@ public static class Strings
         "تطبيق الترقيات تلقائياً عند تثبيت نسخة جديدة"
     );
     public static string SettingsDbReplay   => T("🔁  Rejouer les migrations", "🔁  Replay migrations", "🔁  重新执行迁移", "🔁  เรียกใช้การโยกย้ายอีกครั้ง", "🔁  إعادة تشغيل الترقيات");
+    // ==================== RIGHT NAV SIDEBAR ====================
+    public static string NavLibrary       => T("Bibliothèque", "Library",       "库",          "ห้องสมุด",       "المكتبة");
+    public static string NavReport        => T("Statistiques", "Reports",       "统计",         "รายงาน",         "التقارير");
+    public static string NavDocumentation => T("Documentation", "Documentation","文档",         "เอกสาร",         "التوثيق");
+
+    public static string SettingsReportUrl    => T("URL de l'outil de reporting local", "Local reporting tool URL", "本地报告工具 URL", "URL ของเครื่องมือรายงานในเครื่อง", "عنوان أداة التقارير المحلية");
+    public static string SettingsDocsUrl      => T("URL de la documentation",          "Documentation URL",       "文档 URL",        "URL ของเอกสาร",                "عنوان التوثيق");
+    public static string DocsPlaceholder      => T(
+        "Aucune URL de documentation configurée.\n\nVa dans Paramètres → Avancés → Base de données pour pointer vers la documentation locale ou en ligne.",
+        "No documentation URL configured.\n\nGo to Settings → Advanced → Database to point to local or online documentation.",
+        "未配置文档 URL。\n\n前往 设置 → 高级 → 数据库 以指向本地或在线文档。",
+        "ยังไม่ได้กำหนด URL เอกสาร\n\nไปที่ การตั้งค่า → ขั้นสูง → ฐานข้อมูล เพื่อชี้ไปยังเอกสารในเครื่องหรือออนไลน์",
+        "لم يتم تكوين عنوان التوثيق.\n\nاذهب إلى الإعدادات → متقدم → قاعدة البيانات للإشارة إلى التوثيق المحلي أو عبر الإنترنت."
+    );
+    public static string WebViewLoadError(string url, string detail) => T(
+        $"Impossible de charger {url}\n\n{detail}\n\nVérifie que XAMPP est démarré et que l'URL est correcte (Paramètres → Avancés).",
+        $"Could not load {url}\n\n{detail}\n\nCheck that XAMPP is running and the URL is correct (Settings → Advanced).",
+        $"无法加载 {url}\n\n{detail}\n\n请检查 XAMPP 是否正在运行以及 URL 是否正确（设置 → 高级）。",
+        $"ไม่สามารถโหลด {url}\n\n{detail}\n\nตรวจสอบว่า XAMPP กำลังทำงานและ URL ถูกต้อง (ตั้งค่า → ขั้นสูง)",
+        $"تعذر تحميل {url}\n\n{detail}\n\nتأكد من تشغيل XAMPP وأن العنوان صحيح (الإعدادات → متقدم)."
+    );
+
     public static string SettingsAdvanced   => T(
         "▸  PARAMÈTRES AVANCÉS (serveur, installation, base de données, logs)",
         "▸  ADVANCED SETTINGS (server, installation, database, logs)",