[Performance] Optimize "Scan" page rendering (Camera FAB → Create expense w/ Scan)

[Julesssss]

Problem

Navigating from the Camera FAB to the "Create expense w/ Scan" page feels sluggish. The rendering of the Scan page itself is a bottleneck in the overall create-expense-via-scan flow.

Goal

Profile and optimize the rendering of the Scan page to reduce the transition time from tapping the Camera FAB to the scan page being fully interactive (camera initialized and ready).

Plan:

• Add sentry tracking spans for the flow
• Build sentry dashboard
• Deep investigation into problematic areas and anywhere we can reduce rendering time and improve app performence on web and mobile platforms

Related

• [Metrics] Create Expense flows #81849 — parent tracking issue for Create Expense flow metrics

[Julesssss]

Note from marc that the permissions check could possibly be cached. It was taking ~100ms on iOS dev.

Context: https://expensify.slack.com/archives/C03TBKRSB/p1772060029356039?thread_ts=1771887714.131779&cid=C03TBKRSB

[marcaaron]

Might be helpful to know that we do have a metric for this one:

Query: span.op:ManualOpenCreateExpense iou_request_type:scan (os.name:iOS OR os.name:Android )

But it does not tell us what the origin is e.g. did we get here from the Global Create? Or the Camera FAB? Not sure if that makes a huge difference in practice - but something that came to mind.

[Julesssss]

Created an issue here to add a tracking param for the source of the Create Expense flow.

@rinej may be helping with improving this 👋 🎉