fix(fe): gate pending/resuming channel layouts on channel establishment

Children access $establishedChannelStore which throws if the channel
isn't set yet. Gate rendering on $channelStore !== undefined to ensure
the channel is established before children mount.

Author: sea-snake

src/frontend/src/routes/(new-styling)/(pending-channel)/+layout.svelte

@@ -13,4 +13,6 @@
   });
 </script>
 
-{@render children()}
+{#if $channelStore !== undefined}
+  {@render children()}
+{/if}

src/frontend/src/routes/(new-styling)/(resuming-channel)/+layout.svelte

@@ -25,7 +25,7 @@
   });
 </script>
 
-{#if pendingChannelOrigin !== null}
+{#if pendingChannelOrigin !== null && $channelStore !== undefined}
   {@render children()}
 {:else}
   <Dialog>