Fix database sidebar not appearing on client-side navigation

The subNavigation variable was being reactively assigned from page.data
in both shell.svelte and navigation.svelte, connected via bind:. This
competing reactive ownership caused the value to not update properly
during client-side navigation (only on full page refresh). Made
shell.svelte the single source of truth by removing the duplicate
reactive assignment from navigation.svelte and switching from bind: to
one-way prop passing.

https://claude.ai/code/session_012QCz2xVatAtJ3Q6FSp1cB4

src/lib/layout/navigation.svelte

@@ -1,11 +1,8 @@
 <script lang="ts">
-    import { page } from '$app/state';
     import { getContext } from 'svelte';
     import type { Writable } from 'svelte/store';
 
     export let subNavigation;
-
-    $: subNavigation = page.data.subNavigation;
     // We need to have this second variable, because we only want narrow
     // to change automatically if we change from having a second side nav to
     // not having one, not when the second side nav changes to a different value.

src/lib/layout/shell.svelte

@@ -235,14 +235,14 @@
                 project={activeProject}
                 progressCard={getProgressCard()}
                 avatar={navbarProps.avatar}
-                bind:subNavigation
+                {subNavigation}
                 bind:sideBarIsOpen={$isSidebarOpen}
                 bind:showAccountMenu
                 bind:state />
         {/if}
 
         {#if !$showOnboardingAnimation}
-            <SideNavigation bind:subNavigation />
+            <SideNavigation {subNavigation} />
         {/if}
     </div>