feat(insights): first isights impemetation

lib/features/insights/presentation/widgets/insights_head.dart

@@ -0,0 +1,70 @@
+import 'package:eatvio_app/features/insights/presentation/widgets/insights_colors.dart';
+import 'package:flutter/material.dart';
+
+/// Крупное число + единица + строка с дельтой.
+class InsightsHead extends StatelessWidget {
+  const InsightsHead({
+    super.key,
+    required this.headline,
+    required this.unit,
+    required this.deltaText,
+    this.isDeltaHighlighted = true,
+  });
+
+  final String headline;
+  final String unit;
+  final String deltaText;
+
+  /// Зелёная дельта при наличии изменения, иначе нейтральный серый.
+  final bool isDeltaHighlighted;
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Row(
+          crossAxisAlignment: CrossAxisAlignment.baseline,
+          textBaseline: TextBaseline.alphabetic,
+          children: [
+            Text(
+              headline,
+              key: const Key('insights_headline'),
+              style: const TextStyle(
+                fontSize: 34,
+                fontWeight: FontWeight.w800,
+                color: InsightsColors.title,
+                height: 1.1,
+              ),
+            ),
+            if (unit.isNotEmpty) ...[
+              const SizedBox(width: 6),
+              Text(
+                unit,
+                style: const TextStyle(
+                  fontSize: 16,
+                  fontWeight: FontWeight.w600,
+                  color: InsightsColors.subtitle,
+                ),
+              ),
+            ],
+          ],
+        ),
+        if (deltaText.isNotEmpty) ...[
+          const SizedBox(height: 4),
+          Text(
+            deltaText,
+            key: const Key('insights_delta'),
+            style: TextStyle(
+              fontSize: 13.5,
+              fontWeight: FontWeight.w700,
+              color: isDeltaHighlighted
+                  ? InsightsColors.positive
+                  : InsightsColors.subtitle,
+            ),
+          ),
+        ],
+      ],
+    );
+  }
+}