feat: create application DTOs

Add data-transfer-object interfaces for the application layer:
upload, file, bucket, S3, and auth domains.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/application/dto/file.ts

@@ -0,0 +1,68 @@
+/**
+ * Public file information response returned by the file-info endpoint.
+ * Mirrors the JSON shape of GET /file/:publicId/info.
+ */
+export interface FileInfoResponse {
+  /** Public, shareable identifier (nanoid) */
+  public_id: string;
+  /** Stored file name */
+  file_name: string;
+  /** MIME type of the stored file */
+  mime_type: string;
+  /** File size in bytes */
+  size_bytes: number;
+  /** High-level file category (e.g. "document", "photo") */
+  file_type: string;
+  /** ISO-8601 timestamp of when the file record was created */
+  created_at: string;
+}
+
+/**
+ * Summary-level file metadata used internally for constructing
+ * upload responses and object listing entries.
+ */
+export interface FileMetadata {
+  /** Public, shareable identifier (nanoid) */
+  publicId: string;
+  /** Telegram file identifier used to retrieve the file from Telegram CDN */
+  telegramFileId: string;
+  /** Telegram unique file identifier (persists across re‑uploads) */
+  telegramFileUniqueId: string;
+  /** Chat ID where the file or archive was stored */
+  storageChatId: number;
+  /** Message ID of the stored file or archive */
+  storageMessageId: number;
+  /** Stored file name */
+  fileName: string;
+  /** MIME type of the stored file */
+  mimeType: string;
+  /** File size in bytes */
+  sizeBytes: number;
+  /** High-level file category */
+  fileType: string;
+  /** Telegram user ID of the uploader; 0 when unknown or system */
+  uploaderId: number;
+  /** Timestamp of file record creation */
+  createdAt: Date | string | number;
+}
+
+/**
+ * Upload response shape returned to API callers.
+ * Mirrors the JSON output of the /api/upload endpoint.
+ */
+export interface UploadResponse {
+  /** Public, shareable identifier */
+  public_id: string;
+  /** Stored file name */
+  file_name: string;
+  /** MIME type */
+  mime_type: string;
+  /** File size in bytes */
+  size_bytes: number;
+  /** High-level file category */
+  file_type: string;
+  /** ISO-8601 creation timestamp */
+  created_at: string;
+  /** Public download URL */
+  download_url: string;
+}