* Don't run migration for Rust crypto if the legacy store is empty
Fixes https://github.com/element-hq/element-web/issues/27447
* Add copyright for the TypeScript files in legacy DB dumps
* Provide a type for the accountPickle we check for before migration
* Remove redundant backup response
This is unused
* Simplify keys response
* Downgrade log message.
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Co-authored-by: Richard van der Hoff <richard@matrix.org>