feat: add FormulaList widget and force unit definitions

lib/ai/formula_list.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+import 'package:d4rt_formulas/formula_models.dart';
+import '../corpus.dart';
+import 'formula_screen.dart';
+
+class FormulaList extends StatelessWidget {
+  final Corpus corpus;
+  final List<Formula> formulas;
+
+  const FormulaList({
+    super.key,
+    required this.corpus,
+    required this.formulas,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return ListView.builder(
+      itemCount: formulas.length,
+      itemBuilder: (context, index) {
+        final formula = formulas[index];
+        return ListTile(
+          title: Text(formula.name),
+          onTap: () {
+            Navigator.push(
+              context,
+              MaterialPageRoute(
+                builder: (context) => FormulaScreen(
+                  formula: formula,
+                  corpus: corpus,
+                ),
+              ),
+            );
+          },
+        );
+      },
+    );
+  }
+}

lib/defaults/units/force.d4rt.units

@@ -0,0 +1,31 @@
+[
+  {
+    "name": "newton",
+    "symbol": "N",
+    "isBase": true
+  },
+  {
+    "name": "kilonewton",
+    "symbol": "kN",
+    "baseUnit": "newton",
+    "factor": 1000
+  },
+  {
+    "name": "meganewton",
+    "symbol": "MN",
+    "baseUnit": "newton",
+    "factor": 1000000
+  },
+  {
+    "name": "dyne",
+    "symbol": "dyn",
+    "baseUnit": "newton",
+    "factor": 0.00001
+  },
+  {
+    "name": "pound-force",
+    "symbol": "lbf",
+    "baseUnit": "newton",
+    "factor": 4.44822
+  }
+]

lib/main.dart

@@ -5,6 +5,7 @@ import 'package:resource_portable/resource.dart' show Resource;
 import 'dart:convert';
 
 import 'ai/formula_screen.dart';
+import 'ai/formula_list.dart';
 import 'corpus.dart';
 import 'defaults/default_corpus.dart';
 
@@ -19,26 +20,9 @@ void main() {
           }
           return Scaffold(
             appBar: AppBar(title: const Text('Formulas')),
-            body: ListView.builder(
-              itemCount: snapshot.data!.getFormulas().length,
-              itemBuilder: (context, index) {
-                final formula = snapshot.data!.getFormulas()[index];
-                return ListTile(
-                  title: Text(formula.name),
-                  subtitle: Text(formula.description ?? ''),
-                  onTap: () {
-                    Navigator.push(
-                      context,
-                      MaterialPageRoute(
-                        builder: (context) => FormulaScreen(
-                          formula: formula,
+            body: FormulaList(
               corpus: snapshot.data!,
-                        ),
-                      ),
-                    );
-                  },
-                );
-              },
+              formulas: snapshot.data!.getFormulas(),
             ),
           );
         }