feat: implement media editing functionality in App component, enhance MediaFormModal for editing, and update MediaItem to trigger edit action

src/lib/MediaFormModal.svelte

@@ -2,7 +2,7 @@
   import type { Media } from './interfaces';
   import { fade, scale } from 'svelte/transition';
 
-  let {show, mode, submitMedia, handleClose} = $props();
+  let {show, mode, submitMedia, handleClose, media: initialMedia} = $props();
   let media: Media = $state({
     title: '',
     type: '',
@@ -14,15 +14,19 @@
   });
   $effect(() => {
     if (show) {
-      media = {
-        title: '',
-        type: '',
-        status: 'plan_to_watch',
-        date: '',
-        rating: 0,
-        platform: '',
-        notes: ''
-      };
+      if (mode === 'edit' && initialMedia) {
+        media = { ...initialMedia };
+      } else {
+        media = {
+          title: '',
+          type: '',
+          status: 'plan_to_watch',
+          date: '',
+          rating: 0,
+          platform: '',
+          notes: ''
+        };
+      }
     }
   });
   const statusOptions = [