fix: do not guard all content in feature flag render guard

Generalizes the audience rendering guard by moving RenderForAudience
to an internal path and extending it with a fallback snippet. This
allows RenderForFeature to explicitly check the feature flag first,
then delegate audience-specific rendering with a clear fallback,
resulting in more modular and composable guard components.

Author: seferturan

projects/client/src/lib/guards/RenderForFeature.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
   import type { FeatureFlag } from "$lib/features/feature-flag/models/FeatureFlag";
   import { useFeatureFlag } from "$lib/features/feature-flag/useFeatureFlag";
-  import RenderFor from "$lib/guards/RenderFor.svelte";
+  import RenderForAudience from "$lib/guards/_internal/RenderForAudience.svelte";
   import type { Snippet } from "svelte";
 
   const {
@@ -19,10 +19,13 @@
   const isFlagEnabled = $derived(isEnabled(flag));
 </script>
 
-<RenderFor {audience}>
-  {#if $isFlagEnabled}
+{#if $isFlagEnabled}
+  <RenderForAudience {audience}>
     {@render enabled()}
-  {:else}
-    {@render children?.()}
-  {/if}
-</RenderFor>
+    {#snippet fallback()}
+      {@render children?.()}
+    {/snippet}
+  </RenderForAudience>
+{:else}
+  {@render children?.()}
+{/if}

projects/client/src/lib/guards/_internal/RenderForAudience.svelte

@@ -2,8 +2,13 @@
   import { useAuth } from "$lib/features/auth/stores/useAuth";
   import { useUser } from "$lib/features/auth/stores/useUser";
   import { IS_DEV } from "$lib/utils/env";
+  import type { Snippet } from "svelte";
 
-  const { children, audience }: ChildrenProps & AudienceProps = $props();
+  type RenderForAudienceProps = ChildrenProps & AudienceProps & {
+    fallback?: Snippet;
+  };
+
+  const { children, audience, fallback }: RenderForAudienceProps = $props();
 
   const { isAuthorized } = useAuth();
   const { user } = useUser();
@@ -22,4 +27,6 @@
 
 {#if isAvailableForAudience}
   {@render children()}
+{:else}
+  {@render fallback?.()}
 {/if}