Design loading UI so one slow query doesn't block a whole page from painting

<context>
Page and its data dependencies, roughly in order of how fast each one resolves: user profile header (fast, cached), order history table (medium), real-time inventory sync status (slow, external API)
The slowest data source on this page: The inventory sync status — it calls a third-party API with ~2s typical latency
</context>

<task>
Design the loading UI for this page using route-level loading.tsx and granular Suspense boundaries, so the page streams in as each piece of data resolves instead of showing one full-page spinner until the slowest fetch finishes.
</task>

<requirements>
- Use loading.tsx at the route segment level for the initial navigation fallback — this automatically wraps the segment in a Suspense boundary, so it should show a skeleton that roughly matches the eventual layout, not a generic spinner.
- Identify which pieces of the page are independent of each other's data (don't need to wait on one another) and wrap each in its own Suspense boundary with its own fallback, so they can resolve and stream in on their own schedule. The slowest data source above should never be awaited at the top of the page component in a way that blocks everything else from rendering.
- Give each Suspense boundary a fallback that's sized and shaped like the real content (a skeleton with matching dimensions), not a generic centered spinner that causes a layout jump when the real content swaps in.
- If a section legitimately needs to wait on another (e.g. a detail panel that needs to know which item was selected first), don't force it into a parallel Suspense boundary — nest it, or leave it sequential, and say so explicitly rather than parallelizing something that has a real dependency.
- Note where this interacts with caching: a Suspense boundary around a component doesn't change whether that component's data is cached — that's a separate decision — it only changes when the browser sees the result.
</requirements>

<output_format>
The page's Suspense structure (as a component tree, fallback components sketched not fully styled), plus a one-line note on which sections are truly independent vs. genuinely sequential.
</output_format>