fix: update styling and structure in various components

- Changed margin class from `my-6` to `mb-6` in ContentRows.svelte for consistent spacing.
- Updated PostCard.svelte to use `$derived` for post properties, enhancing reactivity.
- Refined DeadlineBannerBlock.svelte by removing unnecessary border classes and improving layout for better content alignment.
- Modified Button.svelte to support rendering children directly, enhancing flexibility.
- Added `tabindex="0"` to TabBar.svelte for improved accessibility.
- Fixed textarea closing tag in Textarea.svelte for proper HTML structure.
- Corrected span closing tag in Toggle.svelte for valid markup.

src/lib/ui/Button.svelte

@@ -9,6 +9,7 @@
     loading = false,
     type = 'button' as 'button' | 'submit' | 'reset',
     label = '',
+    children,
   } = $props();
 
   const base =
@@ -40,7 +41,9 @@
   {#if loading}
     <span class="inline-block h-4 w-4 animate-spin rounded-full border-2 border-current border-t-transparent"></span>
     <span>Laden...</span>
+  {:else if children}
+    {@render children()}
   {:else}
-    <slot>{label}</slot>
+    {label}
   {/if}
 </button>

src/lib/ui/TabBar.svelte

@@ -30,6 +30,7 @@
   role="tablist"
   aria-label={labelledBy || 'Tabs'}
   class="flex h-12 border-b border-stein-200"
+  tabindex="0"
   onkeydown={handleKeydown}
 >
   {#each tabs as tab}

src/lib/ui/Textarea.svelte

@@ -44,7 +44,7 @@
     class="min-h-[120px] w-full resize-y rounded-lg border bg-white px-4 py-3 text-base text-stein-800 outline-none placeholder:text-stein-400 {error || invalid
       ? 'border-error ring-2 ring-error-subtle'
       : 'border-stein-300 hover:border-stein-400 focus:border-wald-500 focus:ring-2 focus:ring-wald-100'} disabled:bg-stein-100 disabled:opacity-60"
-  />
+  ></textarea>
   {#if error}
     <p id={errorId} class="mt-1.5 text-[0.8125rem] text-error" role="alert">
       {error}

src/lib/ui/Toggle.svelte

@@ -21,7 +21,7 @@
     />
     <span
       class="absolute top-0.5 inline-block h-5 w-5 rounded-full bg-white shadow-sm transition-transform duration-200 {checked ? 'left-[22px] translate-x-0.5' : 'left-0.5'}"
-    />
+    ></span>
   </span>
   {#if label}
     <span class="text-base text-stein-700">{label}</span>