feat: polished admin UI styles + email channels admin CRUD

- Extract inline styles to wwwroot/css/admin.css
- Bootstrap Icons for nav and buttons
- Styled page headers, table, empty state, readonly fields
- Email Channels admin: list, create, edit, delete
- GetAllEmailChannelsQuery + handler
- AdminChannelsController with full CRUD
- form id + form= attribute pattern for EditorLayout footer buttons

Ref: IT-628

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

HrynCo.NotificationService.Web/Views/AdminChannels/Edit.cshtml

@@ -0,0 +1,141 @@
+@using HrynCo.NotificationService.DAL.Abstract.Providers
+@using HrynCo.NotificationService.Web.Controllers.Admin.ViewModels
+@model EmailChannelEditViewModel
+@{
+    Layout = "~/Views/Shared/_EditorLayout.cshtml";
+    ViewData["Title"] = Model.PageTitle;
+    ViewData["EditorTitle"] = Model.PageTitle;
+}
+
+<form id="channelForm" asp-action="Save" asp-controller="AdminChannels" method="post">
+    @Html.AntiForgeryToken()
+    <input asp-for="Id" type="hidden" />
+
+    @if (!ViewData.ModelState.IsValid)
+    {
+        <div class="alert alert-danger mb-3">
+            @foreach (var error in ViewData.ModelState.Values.SelectMany(v => v.Errors))
+            {
+                <div>@error.ErrorMessage</div>
+            }
+        </div>
+    }
+
+    @* Channel Settings section *@
+    <div class="form-section-title"><i class="bi bi-sliders me-1"></i> Channel Settings</div>
+
+    <div class="mb-4">
+        <label asp-for="ServiceName" class="form-label fw-semibold">Service Name</label>
+        <input asp-for="ServiceName" class="form-control" readonly="@(!Model.IsNew)" />
+        <span asp-validation-for="ServiceName" class="text-danger small"></span>
+    </div>
+
+    <div class="row mb-4">
+        <div class="col-md-4">
+            <label asp-for="Priority" class="form-label fw-semibold">Priority</label>
+            <input asp-for="Priority" class="form-control" type="number" min="1" />
+            <span asp-validation-for="Priority" class="text-danger small"></span>
+        </div>
+        <div class="col-md-4">
+            <label asp-for="EmailChannelType" class="form-label fw-semibold">Channel Type</label>
+            <select asp-for="EmailChannelType" class="form-select"
+                    asp-items="Html.GetEnumSelectList<EmailChannelType>()">
+            </select>
+        </div>
+        <div class="col-md-4 d-flex align-items-end">
+            <div class="form-check mb-2">
+                <input asp-for="IsActive" class="form-check-input" type="checkbox" />
+                <label asp-for="IsActive" class="form-check-label fw-semibold">Active</label>
+            </div>
+        </div>
+    </div>
+
+    <div class="row mb-4">
+        <div class="col-md-4">
+            <label asp-for="DailyLimit" class="form-label fw-semibold">Daily Limit</label>
+            <input asp-for="DailyLimit" class="form-control" type="number" min="0" placeholder="Unlimited" />
+            <span asp-validation-for="DailyLimit" class="text-danger small"></span>
+        </div>
+        <div class="col-md-4">
+            <label asp-for="MonthlyLimit" class="form-label fw-semibold">Monthly Limit</label>
+            <input asp-for="MonthlyLimit" class="form-control" type="number" min="0" placeholder="Unlimited" />
+            <span asp-validation-for="MonthlyLimit" class="text-danger small"></span>
+        </div>
+        <div class="col-md-4">
+            <label asp-for="WarnThresholdPercent" class="form-label fw-semibold">Warn Threshold (%)</label>
+            <input asp-for="WarnThresholdPercent" class="form-control" type="number" min="1" max="100" />
+            <span asp-validation-for="WarnThresholdPercent" class="text-danger small"></span>
+        </div>
+    </div>
+
+    @* SMTP Settings section *@
+    <div class="form-section-title mt-4"><i class="bi bi-envelope-at me-1"></i> SMTP Settings</div>
+
+    <div class="row mb-4">
+        <div class="col-md-9">
+            <label asp-for="Host" class="form-label fw-semibold">Host</label>
+            <input asp-for="Host" class="form-control" placeholder="smtp.example.com" />
+            <span asp-validation-for="Host" class="text-danger small"></span>
+        </div>
+        <div class="col-md-3">
+            <label asp-for="Port" class="form-label fw-semibold">Port</label>
+            <input asp-for="Port" class="form-control" type="number" min="1" max="65535" />
+            <span asp-validation-for="Port" class="text-danger small"></span>
+        </div>
+    </div>
+
+    <div class="row mb-4">
+        <div class="col-md-6">
+            <label asp-for="Username" class="form-label fw-semibold">Username</label>
+            <input asp-for="Username" class="form-control" autocomplete="off" />
+            <span asp-validation-for="Username" class="text-danger small"></span>
+        </div>
+        <div class="col-md-6">
+            <label asp-for="Password" class="form-label fw-semibold">Password</label>
+            <input asp-for="Password" class="form-control" type="password" autocomplete="new-password" />
+            <span asp-validation-for="Password" class="text-danger small"></span>
+        </div>
+    </div>
+
+    <div class="mb-4">
+        <div class="form-check">
+            <input asp-for="UseSsl" class="form-check-input" type="checkbox" />
+            <label asp-for="UseSsl" class="form-check-label fw-semibold">Use SSL/TLS</label>
+        </div>
+    </div>
+
+    <div class="row mb-4">
+        <div class="col-md-6">
+            <label asp-for="FromEmail" class="form-label fw-semibold">From Email</label>
+            <input asp-for="FromEmail" class="form-control" type="email" placeholder="noreply@example.com" />
+            <span asp-validation-for="FromEmail" class="text-danger small"></span>
+        </div>
+        <div class="col-md-6">
+            <label asp-for="FromName" class="form-label fw-semibold">From Name</label>
+            <input asp-for="FromName" class="form-control" placeholder="My Service" />
+            <span asp-validation-for="FromName" class="text-danger small"></span>
+        </div>
+    </div>
+
+    <div class="row mb-4">
+        <div class="col-md-6">
+            <label asp-for="AppDisplayName" class="form-label fw-semibold">App Display Name</label>
+            <input asp-for="AppDisplayName" class="form-control" />
+            <span asp-validation-for="AppDisplayName" class="text-danger small"></span>
+        </div>
+        <div class="col-md-6">
+            <label asp-for="AppBaseUrl" class="form-label fw-semibold">App Base URL</label>
+            <input asp-for="AppBaseUrl" class="form-control" placeholder="https://example.com" />
+            <span asp-validation-for="AppBaseUrl" class="text-danger small"></span>
+        </div>
+    </div>
+
+    @section FormActions {
+        <button type="submit" form="channelForm" class="btn btn-primary">
+            <i class="bi bi-floppy me-1"></i> Save
+        </button>
+        <a href="/admin/channels" class="btn btn-secondary">
+            <i class="bi bi-x-lg me-1"></i> Cancel
+        </a>
+    }
+</form>