feat: 초기 프로젝트 설정 및 LunchPick 앱 구현

LunchPick(오늘 뭐 먹Z?) Flutter 앱의 초기 구현입니다.

주요 기능:
- 네이버 지도 연동 맛집 추가
- 랜덤 메뉴 추천 시스템
- 날씨 기반 거리 조정
- 방문 기록 관리
- Bluetooth 맛집 공유
- 다크모드 지원

기술 스택:
- Flutter 3.8.1+
- Riverpod 상태 관리
- Hive 로컬 DB
- Clean Architecture

🤖 Generated with Claude Code

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

lib/core/utils/distance_calculator.dart

@@ -0,0 +1,110 @@
+import 'dart:math' as math;
+
+class DistanceCalculator {
+  static const double earthRadiusKm = 6371.0;
+
+  static double calculateDistance({
+    required double lat1,
+    required double lon1,
+    required double lat2,
+    required double lon2,
+  }) {
+    final double dLat = _toRadians(lat2 - lat1);
+    final double dLon = _toRadians(lon2 - lon1);
+
+    final double a = math.sin(dLat / 2) * math.sin(dLat / 2) +
+        math.cos(_toRadians(lat1)) *
+            math.cos(_toRadians(lat2)) *
+            math.sin(dLon / 2) *
+            math.sin(dLon / 2);
+
+    final double c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a));
+
+    return earthRadiusKm * c;
+  }
+
+  static double _toRadians(double degree) {
+    return degree * (math.pi / 180);
+  }
+
+  static String formatDistance(double distanceInKm) {
+    if (distanceInKm < 1) {
+      return '${(distanceInKm * 1000).round()}m';
+    } else if (distanceInKm < 10) {
+      return '${distanceInKm.toStringAsFixed(1)}km';
+    } else {
+      return '${distanceInKm.round()}km';
+    }
+  }
+
+  static bool isWithinDistance({
+    required double lat1,
+    required double lon1,
+    required double lat2,
+    required double lon2,
+    required double maxDistanceKm,
+  }) {
+    final distance = calculateDistance(
+      lat1: lat1,
+      lon1: lon1,
+      lat2: lat2,
+      lon2: lon2,
+    );
+    return distance <= maxDistanceKm;
+  }
+
+  static double? calculateDistanceFromCurrentLocation({
+    required double targetLat,
+    required double targetLon,
+    double? currentLat,
+    double? currentLon,
+  }) {
+    if (currentLat == null || currentLon == null) {
+      return null;
+    }
+
+    return calculateDistance(
+      lat1: currentLat,
+      lon1: currentLon,
+      lat2: targetLat,
+      lon2: targetLon,
+    );
+  }
+
+  static List<T> sortByDistance<T>({
+    required List<T> items,
+    required double Function(T) getLat,
+    required double Function(T) getLon,
+    required double currentLat,
+    required double currentLon,
+  }) {
+    final List<T> sortedItems = List<T>.from(items);
+    
+    sortedItems.sort((a, b) {
+      final distanceA = calculateDistance(
+        lat1: currentLat,
+        lon1: currentLon,
+        lat2: getLat(a),
+        lon2: getLon(a),
+      );
+      
+      final distanceB = calculateDistance(
+        lat1: currentLat,
+        lon1: currentLon,
+        lat2: getLat(b),
+        lon2: getLon(b),
+      );
+      
+      return distanceA.compareTo(distanceB);
+    });
+    
+    return sortedItems;
+  }
+
+  static Map<String, double> getDefaultLocationForKorea() {
+    return {
+      'latitude': 37.5665,
+      'longitude': 126.9780,
+    };
+  }
+}