feat: add MVC Razor admin UI for email templates

- GetAllEmailTemplatesQuery + handler (new GetAll use case)
- IEmailTemplateRepository.GetAllAsync + EF implementation
- AdminTemplatesController: Index, Create, Edit, Save, Delete
- EmailTemplateEditViewModel with IsNew/PageTitle helpers
- Views/_ViewStart, _ViewImports, Shared/_Layout (Bootstrap 5)
- Shared/_EditorLayout (chained layout for all edit screens)
- Views/AdminTemplates/Index (table with edit/delete actions)
- Views/AdminTemplates/Edit (card form, readonly composite key on edit)
- Program.cs: AddControllersWithViews, UseStaticFiles, MapDefaultControllerRoute

Ref: IT-634

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

HrynCo.NotificationService.Web/Views/AdminTemplates/Index.cshtml

@@ -0,0 +1,68 @@
+@using HrynCo.NotificationService.DAL.Abstract.Templates
+@model IReadOnlyList<EmailTemplate>
+@{
+    ViewData["Title"] = "Email Templates";
+}
+
+<div class="d-flex justify-content-between align-items-center mb-4">
+    <h2 class="mb-0">📋 Email Templates</h2>
+    <a href="/admin/templates/create" class="btn btn-primary">+ Create New Template</a>
+</div>
+
+@if (!ViewData.ModelState.IsValid)
+{
+    <div class="alert alert-danger">
+        @foreach (var error in ViewData.ModelState.Values.SelectMany(v => v.Errors))
+        {
+            <div>@error.ErrorMessage</div>
+        }
+    </div>
+}
+
+@if (Model is null || Model.Count == 0)
+{
+    <div class="alert alert-info">No email templates found.</div>
+}
+else
+{
+    <div class="card shadow-sm">
+        <div class="table-responsive">
+            <table class="table table-hover mb-0">
+                <thead class="table-dark">
+                    <tr>
+                        <th>Service Name</th>
+                        <th>Key</th>
+                        <th>Language</th>
+                        <th>Subject</th>
+                        <th class="text-end">Actions</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    @foreach (var t in Model)
+                    {
+                        <tr>
+                            <td>@t.ServiceName</td>
+                            <td>@t.Key</td>
+                            <td>@t.LanguageCode</td>
+                            <td>@t.Subject</td>
+                            <td class="text-end">
+                                <a href="/admin/templates/@t.ServiceName/@t.Key/@t.LanguageCode"
+                                   class="btn btn-sm btn-outline-primary me-1">✏️ Edit</a>
+                                <form method="post"
+                                      action="/admin/templates/@t.ServiceName/@t.Key/@t.LanguageCode/delete"
+                                      class="d-inline">
+                                    @Html.AntiForgeryToken()
+                                    <button type="submit"
+                                            class="btn btn-sm btn-outline-danger"
+                                            onclick="return confirm('Delete this template?')">
+                                        🗑️ Delete
+                                    </button>
+                                </form>
+                            </td>
+                        </tr>
+                    }
+                </tbody>
+            </table>
+        </div>
+    </div>
+}