Overwrite entry if better score is entered

Use case: A user saves an entry for an exercise. Shortly after, he manages to do a better entry with higher weight or reps.
The entry should be updated.

For a given date D, given exercise X an entry A with A.weight and A.reps is saved.
A new entry B with date D for exercise X will replace A if B.reps > A.reps or B.weight > A.weight. Otherwise B is not stored.

No file or test is named. Start by locating the entry-saving flow and the data model for date, exercise, weight, and reps; verify how existing entries are looked up. Done means a same-date, same-exercise entry is retained only when its weight or reps is higher, with other entries unaffected.

Written by the indexing model from the issue text.