Allow coaches to add and name custom charts on the Client Profile dashboard so we can track metrics beyond the defaults. The current charts are fixed. We can see RHR, weight, body fat, lean mass, calories, steps, etc. but we cannot add key metrics tied to our programming. This forces workarounds in notes or external spreadsheets, which fragments data and slows reviews.

Proposed Solution:
1. Enable "Add chart" on the client profile,
2. Coach selects a metric type: number, time or percentage
3. Coach names the metric (peak HR, HRR 60s), picks units, and chooses data source: manual entry
4. Chart displays trend line with date filters and simple stats

Criteria:
1. Coaches can create up to 5 custom charts per client
2. Units support bpm, seconds, mins, kg, lbs, percent
3. Manual entry

This small feature would eliminate spreadsheets, improve testing workflows, and make trainerize the single source for client progress.