Feature Request: Add Progression Calculation Based on Initial RIR=0 Value

[JinstBF]

Motivation

I would like to suggest to include a popular way of planing progression workouts based on percentage-based progression calculations using an initial RiR = 0 weight value.

Currently, there's no way in wger to directly define a progression based on an RiR=0 baseline weight.
This limits the flexibility for planning effective periodized training.

Proposed Feature

Allow users to:
Input a starting weight where RiR = 0 (e.g., 100 kg for 1 rep) and define a week-by-week progression using percentage values, such as:
- Week 1: 70% → 70 kg
- Week 2: 75% → 75 kg
- Week 3: 80% → 80 kg
- Week 4: 75% → 75 kg
- ...
This would enable template-based routines that scale automatically based on personal max values without requiring manual weight calculation every week.

Implementation Suggestion

Add an input field for entering the RiR = 0 weight.
Extend the existing dropdown (where users define how values are applied) with a new mode.
This new mode would apply the weekly percentage to the base weight and then Replace, Add, or Subtract from the calculated value as needed.