Add auth service, storage service, types, and logging middleware

- Auth service: hashPassword/verifyPassword via bcrypt
- Storage service: saveFile, getFilePath, deleteStoredFile with ENOENT handling
- Types: JwtPayload interface
- Logging middleware: createLogger writing AUTH_FAILURE, AUTH_SUCCESS, FILE_NOT_FOUND
- 27 tests passing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/types.ts

@@ -0,0 +1,4 @@
+export interface JwtPayload {
+  sub: number;
+  username: string;
+}