fix: hotfix facilities filter

1. the let:ariaLabelledBy directive was placed wrongly, it is meant to expose a variable to the template of the slot consumer, and should be defined therein https://svelte.dev/docs/special-elements#slot-slot-key-value (not as a parent component attribute). It's possible the recent a Svelte upgrade made this wrong syntax break.
2. the TopNav z-index made the top nav appear over the modal on desktop. It might have been needed before, but since we dynamically pushed down the map frame below the top nav on desktop (no more overlap), it shouldn't be needed anymore.

src/lib/components/Garden/FacilitiesFilter.svelte

@@ -49,6 +49,7 @@
 
   let vw;
 
+  // Stick the modal to the bottom on mobile
   $: {
     if (vw < maxWidth) {
       stickToBottom = true;
@@ -68,9 +69,8 @@
   {stickToBottom}
   nopadding={stickToBottom}
   ariaLabelledBy="title"
-  let:ariaLabelledBy
 >
-  <div slot="title" class="gardenFilterTitleSection" id={ariaLabelledBy}>
+  <div slot="title" class="gardenFilterTitleSection" let:ariaLabelledBy id={ariaLabelledBy}>
     <h2 id="gardenFilterTitle">{$_('garden.filter.title')}</h2>
   </div>
   <div slot="body" class="gardenFilterBodySection">

src/lib/components/Nav/Top/TopNav.svelte

@@ -81,6 +81,7 @@
   <!-- TODO: Maybe replace later with: https://github.com/sveltejs/svelte/issues/3105#issuecomment-1440443254 -->
   <!-- !important is necessary because the svelte component-scoped CSS otherwise has higher CSS specificity -->
   {#if $user?.superfan}
+    <!-- Hide the extra bar -->
     <!-- Hide the extra bar -->
     <style>
       .nav-extra {
@@ -108,7 +109,6 @@
     width: 100%;
     display: flex;
     flex-direction: column;
-    z-index: 110;
     background-color: var(--color-white);
     box-shadow: 0 0 3.3rem rgba(0, 0, 0, 0.1);
   }

src/lib/components/UI/Modal.svelte

@@ -92,6 +92,7 @@
           {ariaLabelledBy} inserts an "arialabelledby" attribute (which is not a valid ARIA attribute) 
           but it also propagates the given value of ariaLabelledBy back to the let:ariaLabelledBy property on the parent,
           so it can be used within slots by component users without repeating the concrete value of ariaLabelledBy. 
+          https://svelte.dev/docs/special-elements#slot-slot-key-value
         -->
         <slot name="title" {ariaLabelledBy} class="modal-title" />
         {#if closeButton}