Dashboard sidebar animation fix (#1601)

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<!-- This is an auto-generated description by cubic. -->
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## Summary by cubic
Fixes the project sidebar animation flicker by always applying
overflow-hidden to the animated container and only toggling h-0 when
collapsed. Expanding and collapsing sections now animate smoothly
without content popping.

<sup>Written for commit 7af633b1e7.
Summary will update on new commits.</sup>

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<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

* **Bug Fixes**
* Improved the visual clipping behavior of nested sidebar items during
expand/collapse transitions for smoother animations.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/dashboard/src/app/(main)/(protected)/projects/[projectId]/sidebar-layout.tsx

@@ -319,8 +319,8 @@ function NavItem({
               : "0px",
           }}
           className={cn(
-            "ml-[0.5px] w-[calc(100%-1px)] transition-[height] duration-200",
-            !isExpanded && "h-0 overflow-hidden"
+            "ml-[0.5px] w-[calc(100%-1px)] overflow-hidden transition-[height] duration-200",
+            !isExpanded && "h-0"
           )}
         >
           <div className="space-y-2 py-2 pl-3">