Improve reliability of import CSV feature

[notsidney]

Is your feature request related to a problem? Please describe.
Currently, when importing from CSV, rows are added on the frontend. This allows the feature to respect any access control restrictions placed on the user doing the import and ensure the same audit fields are written if enabled.

But since rows are written one at a time, it can take a long time to complete the process, and an app crash can stop the import midway, forcing users to go through the import wizard again.

Describe the solution you'd like
Firestore batched writes are a potential solution, but we haven’t explored them yet.

Additional context
On Discord: https://discord.com/channels/853498675484819476/864878815544475648/922508526499270737