feat: add local-first private AI digest workflow

Migrate app code into canonical feature slices, add phone-only AI digest scheduling and review, wire local notification/background task support, and cover the flow with tests.

lib/core/presentation/frosted_card.dart

@@ -0,0 +1,40 @@
+import 'dart:ui';
+
+import 'package:flutter/material.dart';
+
+class FrostedCard extends StatelessWidget {
+  const FrostedCard({
+    required this.child,
+    super.key,
+    this.padding = const EdgeInsets.all(20),
+  });
+
+  final Widget child;
+  final EdgeInsetsGeometry padding;
+
+  @override
+  Widget build(BuildContext context) {
+    return ClipRRect(
+      borderRadius: BorderRadius.circular(24),
+      child: BackdropFilter(
+        filter: ImageFilter.blur(sigmaX: 12, sigmaY: 12),
+        child: Container(
+          padding: padding,
+          decoration: BoxDecoration(
+            color: Colors.white.withValues(alpha: 0.72),
+            borderRadius: BorderRadius.circular(24),
+            border: Border.all(color: Colors.white.withValues(alpha: 0.6)),
+            boxShadow: const <BoxShadow>[
+              BoxShadow(
+                color: Color(0x14000000),
+                blurRadius: 24,
+                offset: Offset(0, 12),
+              ),
+            ],
+          ),
+          child: child,
+        ),
+      ),
+    );
+  }
+}