refactor(routes): canonical URLs now match sablog format exactly

- /show-{id}.shtml (comments page: /show-{id}-{page}.shtml)
- /category-{cid}.shtml / /category-{cid}-{page}.shtml
- /archives-{YYYYMM}.shtml / /archives-{YYYYMM}-{page}.shtml
- /tag/{name}, /tagslist.shtml, /index-{page}.shtml
- slug 时代的 /posts/{slug} 等旧格式全部 301 到 sablog 格式

app/Models/Post.php

@@ -104,7 +104,7 @@ class Post extends Model implements HasMedia
 
     public function getUrlAttribute(): string
     {
-        return route('posts.show', $this->slug ?? $this->id);
+        return route('posts.show', $this->id);
     }
 
     /**