feat(fitness/body-parts): "Same as last" button + larger Copy L→R pill

- New "Same as last" pill below each step's stepper. Clicking fills
  the input(s) with the prior recorded value(s) — for paired steps
  in split mode, both L and R — and advances to the next step.
  Only rendered when a previous measurement exists; the placeholder
  already surfaces the exact number so the button text stays terse.
- Copy L→R button resized to match the same-as-last pill (0.88 rem
  text, 0.55 × 1.1 rem padding) and given top margin. Unicode →
  swapped for a proper ArrowRight icon between L and R.
- i18n: added `same_as_last` and split `copy_l_to_r` into
  `copy_l_to_r_before` / `copy_l_to_r_after` so each language keeps
  its natural wrapping around the arrow (EN "Copy L / R",
  DE "L / R übernehmen").

TODO.md

@@ -4,9 +4,10 @@
 [x] on /fitness/measure, fill "Past measurements" in SSR only for the last 10 measurements. anything further should be fetched client side on mount to decreae initial page load time. use a "show more" button and paginate measurments.
 [x] on /fitness/measure (resp. their associated logging API routes), consolidate measurements by day. If we want to log another measurement, overwriting an old one, show a warning to indicate this. disparate measurements (e.g., weight and bodyfat) should not show this warning but simply be merged into one log entry for that day.
 [x] on /fitness/measure in the past measurments tab, show more than "Body measurements only" if we don't have Bodyweight logged. we can be a bit more elaborate in our syntax here tbh.
-[ ] add a button on /fitness/measure/body-parts for each measurement directly below to say "Same value", instead of having to hit +, then - to lock in same number
+[x] add a button on /fitness/measure/body-parts for each measurement directly below to say "Same value", instead of having to hit +, then - to lock in same number
 [ ] BF graph (with trend line like weight graph) on /fitness/stats page. Emphasize relative changes, not absolute numbers in design (as we cannot trust those) (e.g., use start day of overview as 0% and then show +/- x % on the graph)
 [ ] Workshop better names than "Measure" for the /fitness/measure route. It's about body data points (i.e., non-food related). What's a better, short name than "Measure" to capture the logging of weight, body composition, body part measurements, and period tracking?
+[ ] on /fitness/stats/histoy/<part> for body measurement graphs, make the range reasonable. e.g., if we have 1 cm change, do not fill the entire y-height with 1 cm. Use reasonable padding for low ranges (i think we do something like htis already on the weight graph?)
 
 ## Refactor Recipe Search Component