아이폰 근접센서 주머니 감시, 학생 목록 타일 UI, 학교 서버 주소 반영

- iOS는 조도 센서/백그라운드 서비스가 불가능해서 근접센서(UIDevice
  proximityMonitoring) + 가이드 접근 안내로 대체 구현 (Core NFC와 마찬가지로
  네이티브 플러그인 필요해서 ProximityMonitorPlugin.swift 추가)
- 교사 대시보드 실시간 출석 현황: 모바일 리스트/데스크톱 표를 타일 그리드로
  통일해서 한눈에 보기 쉽게 변경
- 서버를 학교 자체 서버(Cloudflare Tunnel, api.backsanhi.shop)로 이전하면서
  기본 BASE_URL 갱신
- Firebase CLI 로컬 캐시(.firebase/)는 소스가 아니라 gitignore 처리

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

ios/Runner.xcodeproj/project.pbxproj

@@ -11,6 +11,7 @@
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 		74858FAF1ED2DC5600515810 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 74858FAE1ED2DC5600515810 /* AppDelegate.swift */; };
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 		7884E8682EC3CC0700C636F2 /* SceneDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7884E8672EC3CC0400C636F2 /* SceneDelegate.swift */; };
 		78A318202AECB46A00862997 /* FlutterGeneratedPluginSwiftPackage in Frameworks */ = {isa = PBXBuildFile; productRef = 78A3181F2AECB46A00862997 /* FlutterGeneratedPluginSwiftPackage */; };
 		97C146FC1CF9000F007C117D /* Main.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 97C146FA1CF9000F007C117D /* Main.storyboard */; };
@@ -49,6 +50,7 @@
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 		74858FAE1ED2DC5600515810 /* AppDelegate.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
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 		7884E8672EC3CC0400C636F2 /* SceneDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SceneDelegate.swift; sourceTree = "<group>"; };
 		78E0A7A72DC9AD7400C4905E /* FlutterGeneratedPluginSwiftPackage */ = {isa = PBXFileReference; lastKnownFileType = wrapper; name = FlutterGeneratedPluginSwiftPackage; path = Flutter/ephemeral/Packages/FlutterGeneratedPluginSwiftPackage; sourceTree = "<group>"; };
 		7AFA3C8E1D35360C0083082E /* Release.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = Release.xcconfig; path = Flutter/Release.xcconfig; sourceTree = "<group>"; };
@@ -122,6 +124,7 @@
 				1498D2321E8E86230040F4C2 /* GeneratedPluginRegistrant.h */,
 				1498D2331E8E89220040F4C2 /* GeneratedPluginRegistrant.m */,
 				74858FAE1ED2DC5600515810 /* AppDelegate.swift */,
+				E653BC1DC10E8731479786F7 /* ProximityMonitorPlugin.swift */,
 				7884E8672EC3CC0400C636F2 /* SceneDelegate.swift */,
 				74858FAD1ED2DC5600515810 /* Runner-Bridging-Header.h */,
 			);
@@ -282,6 +285,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				74858FAF1ED2DC5600515810 /* AppDelegate.swift in Sources */,
+				5FA389C5018E5592CC402E5C /* ProximityMonitorPlugin.swift in Sources */,
 				1498D2341E8E89220040F4C2 /* GeneratedPluginRegistrant.m in Sources */,
 				7884E8682EC3CC0700C636F2 /* SceneDelegate.swift in Sources */,
 			);