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/upload.ts

@@ -0,0 +1,46 @@
+/**
+ * Input for the upload file use case.
+ * Carries all metadata needed to persist an uploaded file,
+ * including its temporary location on disk and optional bucket/S3 context.
+ */
+export interface UploadInput {
+  /** Absolute path to the temporary file on disk */
+  tempPath: string;
+  /** SHA-256 hex digest of the file content */
+  fileHash: string;
+  /** Original file name (may include extension) */
+  fileName: string;
+  /** MIME type detected from content inspection or request header */
+  mimeType: string;
+  /** High-level file category (e.g. "document", "photo", "video") */
+  fileType: string;
+  /** File size in bytes */
+  sizeBytes: number;
+  /** Telegram user ID of the uploader; 0 when unknown or system */
+  uploaderId?: number;
+  /** Target bucket UUID for S3-compatible storage; null when un-bucketed */
+  bucketId?: string | null;
+  /** Object key within the bucket for S3-compatible storage; null when un-bucketed */
+  s3Key?: string | null;
+}
+
+/**
+ * Output from the upload file use case.
+ * Contains the public-facing file metadata returned to the caller.
+ */
+export interface UploadOutput {
+  /** Public, shareable identifier (nanoid) */
+  publicId: string;
+  /** Stored file name (may have been normalized with extension) */
+  fileName: string;
+  /** MIME type of the stored file */
+  mimeType: string;
+  /** File size in bytes */
+  sizeBytes: number;
+  /** High-level file category */
+  fileType: string;
+  /** ISO-8601 timestamp of when the file record was created */
+  createdAt: Date;
+  /** Public download URL */
+  downloadUrl: string;
+}