```

refactor: 重命名项目名称从"体己"到"康康"

将整个项目的目录结构从"体己"重命名为"康康"，包括所有源代码文件、
资源文件、测试文件以及Xcode项目配置文件。此更改涉及项目中所有的
文件路径和应用入口点(App/TijiApp.swift → App/KangkangApp.swift)。
```

康康/Persistence/FileVault.swift

@@ -0,0 +1,101 @@
+import Foundation
+import UIKit
+
+enum FileVaultError: Error {
+    case readFailed
+    case writeFailed
+    case removeFailed
+    case decodeFailed
+}
+
+/// `@unchecked Sendable`:rootURL 是 let,方法只 I/O 到沙盒目录(线程安全),
+/// 可被任意 actor / Task 跨边界访问。
+/// `nonisolated(unsafe) shared`:见 ModelStore 同款注释。
+final class FileVault: @unchecked Sendable {
+    nonisolated(unsafe) static let shared: FileVault = {
+        do {
+            let appSupport = try FileManager.default.url(
+                for: .applicationSupportDirectory,
+                in: .userDomainMask,
+                appropriateFor: nil,
+                create: true
+            )
+            let vaultURL = appSupport.appendingPathComponent("Vault", isDirectory: true)
+            return try FileVault(rootURL: vaultURL)
+        } catch {
+            fatalError("FileVault.shared init failed: \(error)")
+        }
+    }()
+
+    let rootURL: URL
+
+    init(rootURL: URL) throws {
+        self.rootURL = rootURL
+        try FileManager.default.createDirectory(
+            at: rootURL,
+            withIntermediateDirectories: true,
+            attributes: [.protectionKey: FileProtectionType.complete]
+        )
+    }
+
+    struct SavedAsset {
+        let relativePath: String
+        let bytes: Int
+    }
+
+    // MARK: - Path Safety
+
+    private func resolveSafePath(_ relativePath: String) throws -> URL {
+        guard !relativePath.contains("/"),
+              !relativePath.contains(".."),
+              !relativePath.isEmpty else {
+            throw FileVaultError.readFailed
+        }
+        let url = rootURL.appendingPathComponent(relativePath)
+        guard url.path.hasPrefix(rootURL.path) else {
+            throw FileVaultError.readFailed
+        }
+        return url
+    }
+
+    // MARK: - Public API
+
+    func writeJPEG(_ image: UIImage, quality: CGFloat = 0.85) throws -> SavedAsset {
+        guard let data = image.jpegData(compressionQuality: quality) else {
+            throw FileVaultError.writeFailed
+        }
+        let filename = "\(UUID().uuidString).jpg"
+        let url = rootURL.appendingPathComponent(filename)
+        try data.write(to: url, options: [.atomic, .completeFileProtection])
+        return SavedAsset(relativePath: filename, bytes: data.count)
+    }
+
+    func loadImage(relativePath: String) throws -> UIImage {
+        let url = try resolveSafePath(relativePath)
+        let data: Data
+        do {
+            data = try Data(contentsOf: url)
+        } catch {
+            throw FileVaultError.readFailed
+        }
+        guard let image = UIImage(data: data) else { throw FileVaultError.decodeFailed }
+        return image
+    }
+
+    func remove(relativePath: String) throws {
+        let url = try resolveSafePath(relativePath)
+        do {
+            try FileManager.default.removeItem(at: url)
+        } catch {
+            throw FileVaultError.removeFailed
+        }
+    }
+
+    func wipe() throws {
+        let fm = FileManager.default
+        let contents = try fm.contentsOfDirectory(at: rootURL, includingPropertiesForKeys: nil)
+        for url in contents {
+            try fm.removeItem(at: url)
+        }
+    }
+}