Paste CSV data

Add an option to either post data for multiple exercises at once or per exercise.
The data could have the format
`exerciseID;date;weight;reps`

Upon saving, for each row the normal calculations (one RM, strength Score) are done.

Additionally it would be useful to provide an export with the same data structure

The issue names no files, tests, or entry points; first inspect the app's exercise and workout logging flows to find where data is entered and saved. Clarify whether the feature should support bulk entry, per-exercise entry, export, or all three, and confirm the expected CSV behavior; done should match the agreed import/export scope and preserve the normal one-rep-max and strength-score calculations for each row.

Written by the indexing model from the issue text.