feat(chat): 채팅 탭 추가 및 캐릭터/톡 내부 탭 구현

- ChatTabView 신설: 앱 바 + 내부 탭(캐릭터/톡) 전환 구성
- 커스텀 탭 적용
  - indicatorHeight: 4, indicatorColor: #3bb9f1
  - tabText color: #b0bec5
  - 폰트: 선택 전 Pretendard-Regular, 선택 후 Pretendard-Bold
- HomeView/BottomTabView에 ChatTabView 연동
- CharacterView/TalkView 플레이스홀더 추가

SodaLive/Sources/Chat/Character/CharacterView.swift

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+//
+//  CharacterView.swift
+//  SodaLive
+//
+//  Created by klaus on 8/29/25.
+//
+
+import SwiftUI
+
+struct CharacterView: View {
+  var body: some View {
+    VStack(spacing: 12) {
+      Spacer()
+      Text("캐릭터 페이지 (준비중)")
+        .font(.custom(Font.preMedium.rawValue, size: 16))
+        .multilineTextAlignment(.center)
+      Spacer()
+    }
+  }
+}
+
+#Preview {
+  CharacterView()
+}

SodaLive/Sources/Chat/ChatTabView.swift

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+//
+//  ChatTabView.swift
+//  SodaLive
+//
+//  Created by klaus on 8/29/25.
+//
+
+import SwiftUI
+
+struct ChatTabView: View {
+    @AppStorage("token") private var token: String = UserDefaults.string(forKey: UserDefaultsKey.token)
+    
+    private enum InnerTab: Int, CaseIterable {
+        case character = 0
+        case talk = 1
+        
+        var title: String {
+            switch self {
+            case .character: return "캐릭터"
+            case .talk: return "톡"
+            }
+        }
+    }
+    
+    @State private var selectedTab: InnerTab = .character
+    
+    var body: some View {
+        VStack(alignment: .leading, spacing: 0) {
+            // 앱 바
+            HStack(spacing: 24) {
+                Image("img_text_logo")
+                
+                Spacer()
+                
+                if !token.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
+                    Image("ic_search_white")
+                        .onTapGesture {
+                            AppState
+                                .shared
+                                .setAppStep(step: .search)
+                        }
+                    
+                    Image("ic_can_circle")
+                        .onTapGesture {
+                            AppState
+                                .shared
+                                .setAppStep(step: .canCharge(refresh: {}))
+                        }
+                }
+            }
+            .padding(.horizontal, 24)
+            .padding(.vertical, 20)
+            
+            // 내부 탭 (캐릭터 / 톡)
+            HStack(spacing: 0) {
+                ChatInnerTab(
+                    title: InnerTab.character.title,
+                    isSelected: selectedTab == .character,
+                    onTap: { if selectedTab != .character { selectedTab = .character } }
+                )
+                
+                ChatInnerTab(
+                    title: InnerTab.talk.title,
+                    isSelected: selectedTab == .talk,
+                    onTap: { if selectedTab != .talk { selectedTab = .talk } }
+                )
+            }
+            .padding(.bottom, 12)
+            
+            Group {
+                switch selectedTab {
+                case .character:
+                    CharacterView()
+                case .talk:
+                    TalkView()
+                }
+            }
+            .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .topLeading)
+        }
+    }
+}
+
+struct ChatInnerTab: View {
+    let title: String
+    let isSelected: Bool
+    let onTap: () -> Void
+    
+    var body: some View {
+        Button(action: onTap) {
+            VStack(spacing: 0) {
+                Spacer()
+                
+                Text(title)
+                    .font(
+                        .custom(
+                            isSelected ? Font.preBold.rawValue : Font.preRegular.rawValue,
+                            size: 18
+                        )
+                    )
+                    .foregroundColor(Color(hex: "b0bec5"))
+                    .frame(maxWidth: .infinity)
+                
+                Spacer()
+                
+                Rectangle()
+                    .frame(maxWidth: .infinity)
+                    .frame(height: 4)
+                    .foregroundColor(Color(hex: "3bb9f1").opacity(isSelected ? 1 : 0))
+            }
+            .frame(height: 50)
+            .contentShape(Rectangle())
+        }
+        .buttonStyle(PlainButtonStyle())
+    }
+}
+
+#Preview {
+    ChatTabView()
+}

SodaLive/Sources/Chat/Talk/TalkView.swift

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+//
+//  TalkView.swift
+//  SodaLive
+//
+//  Created by klaus on 8/29/25.
+//
+
+import SwiftUI
+
+struct TalkView: View {
+  var body: some View {
+    VStack(spacing: 12) {
+      Spacer()
+      Text("톡 페이지 (준비중)")
+        .font(.custom(Font.preMedium.rawValue, size: 16))
+        .multilineTextAlignment(.center)
+      Spacer()
+    }
+  }
+}
+
+#Preview {
+  TalkView()
+}