Increase weight slider precision to ~1 lb increments

Changed divisions from 170 to 374, giving approximately 0.45 kg per
step (~1 lb precision) instead of 1 kg per step (~2.2 lbs).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/screens/baseline_screen.dart

@@ -355,7 +355,7 @@ class _BaselineScreenState extends State<BaselineScreen> {
           value: _weightKg,
           min: 30,
           max: 200,
-          divisions: 170,
+          divisions: 374,
           onChanged: widget.readOnly
               ? null
               : (value) => setState(() => _weightKg = value),