[Nav] Add ثبت آگهی CTA, streamline menu, active-link highlight, role dashboards

Header gets a prominent accent ＋ثبت آگهی CTA → /Employer/Index (auth redirect handles login → register/post). Main nav trimmed to the 5 core public links (خانه/شیفت‌ها/استخدام/مراکز/تقویم); دریافت اپ + راهنما live in the footer and علاقه‌مندی‌ها in the profile menu, so the bar is far less crowded. Added active-page highlight (accent underline on desktop, soft background on mobile). Login now sends admins to /Admin/Overview (dashboard) instead of the ingestion queue; employers→/Employer/Index, job-seekers→/Me already in place.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/JobsMedical.Web/Pages/Shared/_Layout.cshtml

@@ -93,16 +93,14 @@
 
             <div class="nav-collapse">
                 <nav class="main-nav">
-                    <a asp-page="/Index">خانه</a>
-                    <a asp-page="/Shifts/Index" data-tour="shifts">شیفت‌ها</a>
-                    <a asp-page="/Jobs/Index" data-tour="jobs">استخدام</a>
-                    <a asp-page="/Calendar/Index">تقویم هفتگی</a>
-                    <a asp-page="/Download">دریافت اپ</a>
-                    <a asp-page="/Facilities/Index">مراکز درمانی</a>
-                    <a asp-page="/Preferences/Index" data-tour="prefs">علاقه‌مندی‌ها</a>
-                    <a asp-page="/Help" data-tour="help">راهنما</a>
+                    <a asp-page="/Index" class="@(path == "/" ? "active" : null)">خانه</a>
+                    <a asp-page="/Shifts/Index" data-tour="shifts" class="@(path.StartsWith("/Shifts") ? "active" : null)">شیفت‌ها</a>
+                    <a asp-page="/Jobs/Index" data-tour="jobs" class="@(path.StartsWith("/Jobs") ? "active" : null)">استخدام</a>
+                    <a asp-page="/Facilities/Index" class="@(path.StartsWith("/Facilities") ? "active" : null)">مراکز درمانی</a>
+                    <a asp-page="/Calendar/Index" class="@(path.StartsWith("/Calendar") ? "active" : null)">تقویم هفتگی</a>
                 </nav>
                 <div class="header-actions">
+                    <a class="btn btn-accent btn-sm cta-post" asp-page="/Employer/Index" data-tour="post">＋ ثبت آگهی</a>
                     @if (User.Identity?.IsAuthenticated == true)
                     {
                         <a class="nav-action bell-inline js-bell" asp-page="/Me/Notifications" title="اعلان‌ها" data-tour="bell"><span class="bell-ico">🔔</span><span class="bell-label">اعلان‌ها</span>@if (unreadCount > 0) {<span class="bell-badge">@JalaliDate.ToPersianDigits(unreadCount > 99 ? "99+" : unreadCount.ToString())</span>}</a>