Refactor TagList page to inline code-behind logic

Refactor the `TagList` page by moving code-behind logic from `TagList.cshtml.cs` to `TagList.cshtml`. This includes:
- Adding necessary `using` directives
- Injecting `IMediator` dependency
- Implementing `OnGet` method for GET requests
- Removing `@model` directive
- Introducing `@functions` block for properties and methods
- Accessing `Posts` property directly in Razor markup
- Updating `partial` tag helper to use the `Posts` property

src/Moonglade.Web/Pages/TagList.cshtml

@@ -1,5 +1,10 @@
 @page "/tags/{normalizedName:regex(^(?!-)([a-zA-Z0-9-]){{1,32}}$)}"
-@model Moonglade.Web.Pages.TagListModel
+@using Microsoft.AspNetCore.Mvc.TagHelpers
+@using Moonglade.Core.PostFeature
+@using Moonglade.Core.TagFeature
+@using Moonglade.Web.PagedList
+@inject IMediator Mediator
+
 @{
     ViewBag.BodyClass = "body-tag-list bg-gray-1";
 }
@@ -8,13 +13,37 @@
     @ViewBag.TitlePrefix
 </h2>
 
-@if (Model.Posts.Count > 0)
+@if (Posts.Count > 0)
 {
-    <partial name="_PostList" model="Model.Posts" />
+    <partial name="_PostList" model="Posts" />
 }
 else
 {
     <div class="text-muted text-center">
         - @SharedLocalizer["No Posts"] -
     </div>
 }
+
+@functions {
+
+    [BindProperty(SupportsGet = true)]
+    public int P { get; set; } = 1;
+    public BasePagedList<PostDigest> Posts { get; set; }
+
+    public async Task<IActionResult> OnGet(string normalizedName)
+    {
+        var tagResponse = await Mediator.Send(new GetTagQuery(normalizedName));
+        if (tagResponse is null) return NotFound();
+
+        var pagesize = BlogConfig.ContentSettings.PostListPageSize;
+        var posts = await Mediator.Send(new ListByTagQuery(tagResponse.Id, pagesize, P));
+        var count = await Mediator.Send(new CountPostQuery(CountType.Tag, TagId: tagResponse.Id));
+
+        ViewData["TitlePrefix"] = tagResponse.DisplayName;
+
+        var list = new BasePagedList<PostDigest>(posts, P, pagesize, count);
+        Posts = list;
+
+        return Page();
+    }
+}