```mermaid
classDiagram
    class QDR_TSS {
        -plugin_name: string
        -version: string
        -loader: QDR_TSS_Loader
        +__construct()
        +define_constants()
        -load_dependencies()
        -set_locale()
        -define_admin_hooks()
        -define_public_hooks()
        -define_rest_api_hooks()
        -define_cron_hooks()
        +run()
        +get_plugin_name(): string
        +get_loader(): QDR_TSS_Loader
        +get_version(): string
    }

    class QDR_TSS_Loader {
        -actions: array
        -filters: array
        +__construct()
        +add_action(hook, component, callback, priority, accepted_args)
        +add_filter(hook, component, callback, priority, accepted_args)
        -add(hooks, hook, component, callback, priority, accepted_args): array
        +run()
    }

    class QDR_TSS_i18n {
        +load_plugin_textdomain()
    }

    class QDR_TSS_Activator {
        +activate(): static
    }

    class QDR_TSS_Deactivator {
        +deactivate(): static
    }

    class QDR_TSS_DB_Manager {
        -$_instance: QDR_TSS_DB_Manager
        -table_name: string
        +instance(): QDR_TSS_DB_Manager
        +__construct()
        +create_table(): bool
        +get_item(id): object
        +get_item_by_media_id(media_id): object
        +get_items(args): array
        +insert_item(data): int|false
        +update_item(id, data): bool
        +update_item_by_media_id(media_id, data): bool
        +delete_item(id): bool
        +delete_item_by_media_id(media_id): bool
        +get_expired_items(): array
        +delete_expired_items(): int
        +increment_download_count(id): bool
        +get_total_storage(): int
        +would_exceed_storage_limit(file_size, max_size): bool
        -get_column_formats(data): array
    }

    class QDR_TSS_File_Manager {
        -$_instance: QDR_TSS_File_Manager
        +instance(): QDR_TSS_File_Manager
        +__construct()
        +init_file_system(): bool
        +create_dated_directory(date): string|false
        +init_chunked_upload(): string|false
        +store_chunk(upload_id, chunk_index, file): bool
        +check_all_chunks(upload_id, total_chunks): bool
        +finalize_chunked_upload(upload_id, total_chunks, original_filename): array|false
        -combine_chunks(upload_dir, total_chunks, file_path): bool
        -cleanup_chunks(upload_dir): bool
        +delete_file(file_path): bool
        +get_file_size(file_path): int|false
        +cleanup_empty_directories(directory): void
    }

    class QDR_TSS_Settings {
        -$_instance: QDR_TSS_Settings
        -option_name: string
        -defaults: array
        -settings: array
        +instance(): QDR_TSS_Settings
        +__construct()
        +load_settings(): void
        +get_settings(): array
        +get_setting(key, default): mixed
        +update_settings(settings): bool
        +update_setting(key, value): bool
        +generate_api_key(): string
        +validate_api_key(api_key): bool
        +format_bytes(bytes, precision): string
    }

    class QDR_TSS_Cron_Manager {
        -plugin_name: string
        -version: string
        +__construct(plugin_name, version)
        +purge_expired_files(): int
        +manual_purge_expired_files(): int
        +schedule_purge_event(): void
        +unschedule_purge_event(): void
    }

    class QDR_TSS_Admin {
        -plugin_name: string
        -version: string
        +__construct(plugin_name, version)
        +enqueue_styles(): void
        +enqueue_scripts(): void
        +add_admin_menu(): void
        +render_media_page(): void
        +render_settings_page(): void
    }

    class QDR_TSS_Media_Page {
        -plugin_name: string
        -version: string
        -db_manager: QDR_TSS_DB_Manager
        -file_manager: QDR_TSS_File_Manager
        +__construct(plugin_name, version)
        +ajax_get_items(): void
        +ajax_edit_item(): void
        +ajax_delete_item(): void
        +ajax_get_item_details(): void
    }

    class QDR_TSS_Settings_Page {
        -plugin_name: string
        -version: string
        -settings: QDR_TSS_Settings
        -cron_manager: QDR_TSS_Cron_Manager
        +__construct(plugin_name, version)
        +ajax_save_settings(): void
        +ajax_purge_expired(): void
    }

    class QDR_TSS_REST_Controller {
        -plugin_name: string
        -version: string
        -settings: QDR_TSS_Settings
        +__construct(plugin_name, version)
        +register_routes(): void
        +check_api_key(result): WP_Error|null
        +check_rest_permission(): bool
        -get_all_headers(): array
    }

    class QDR_TSS_Media_Controller {
        -plugin_name: string
        -version: string
        -namespace: string
        -base: string
        -db_manager: QDR_TSS_DB_Manager
        -file_manager: QDR_TSS_File_Manager
        +__construct(plugin_name, version)
        +register_routes(): void
        +check_permission(): bool
        +get_items(request): WP_REST_Response|WP_Error
        +get_item(request): WP_REST_Response|WP_Error
        +update_item(request): WP_REST_Response|WP_Error
        +delete_item(request): WP_REST_Response|WP_Error
    }

    class QDR_TSS_Upload_Controller {
        -plugin_name: string
        -version: string
        -namespace: string
        -db_manager: QDR_TSS_DB_Manager
        -file_manager: QDR_TSS_File_Manager
        -settings: QDR_TSS_Settings
        +__construct(plugin_name, version)
        +register_routes(): void
        +check_permission(): bool
        +init_chunked_upload(request): WP_REST_Response|WP_Error
        +upload_chunk(request): WP_REST_Response|WP_Error
        +finalize_chunked_upload(request): WP_REST_Response|WP_Error
    }

    class QDR_TSS_Public {
        -plugin_name: string
        -version: string
        +__construct(plugin_name, version)
        +enqueue_styles(): void
        +enqueue_scripts(): void
        +create_download_page(): void
    }

    class QDR_TSS_Shortcode {
        -plugin_name: string
        -version: string
        -download: QDR_TSS_Download
        +__construct(plugin_name, version)
        +register_shortcodes(): void
        +download_shortcode(atts): string
    }

    class QDR_TSS_Download {
        -plugin_name: string
        -version: string
        -db_manager: QDR_TSS_DB_Manager
        -file_manager: QDR_TSS_File_Manager
        +__construct(plugin_name, version)
        +process_download_request(atts): string
        -render_download_form(media_id): string
    }

    %% Relationships
    QDR_TSS --> QDR_TSS_Loader : uses
    QDR_TSS --> QDR_TSS_i18n : uses
    QDR_TSS --> QDR_TSS_Admin : uses
    QDR_TSS --> QDR_TSS_Public : uses
    QDR_TSS --> QDR_TSS_REST_Controller : uses
    QDR_TSS_Activator --> QDR_TSS_DB_Manager : uses
    QDR_TSS_Activator --> QDR_TSS_File_Manager : uses
    QDR_TSS_Activator --> QDR_TSS_Settings : uses
    QDR_TSS_Admin --> QDR_TSS_Media_Page : uses
    QDR_TSS_Admin --> QDR_TSS_Settings_Page : uses
    QDR_TSS_Media_Page --> QDR_TSS_DB_Manager : uses
    QDR_TSS_Media_Page --> QDR_TSS_File_Manager : uses
    QDR_TSS_Settings_Page --> QDR_TSS_Settings : uses
    QDR_TSS_Settings_Page --> QDR_TSS_Cron_Manager : uses
    QDR_TSS_REST_Controller --> QDR_TSS_Media_Controller : uses
    QDR_TSS_REST_Controller --> QDR_TSS_Upload_Controller : uses
    QDR_TSS_REST_Controller --> QDR_TSS_Settings : uses
    QDR_TSS_Media_Controller --> QDR_TSS_DB_Manager : uses
    QDR_TSS_Media_Controller --> QDR_TSS_File_Manager : uses
    QDR_TSS_Upload_Controller --> QDR_TSS_DB_Manager : uses
    QDR_TSS_Upload_Controller --> QDR_TSS_File_Manager : uses
    QDR_TSS_Upload_Controller --> QDR_TSS_Settings : uses
    QDR_TSS_Public --> QDR_TSS_Shortcode : uses
    QDR_TSS_Shortcode --> QDR_TSS_Download : uses
    QDR_TSS_Download --> QDR_TSS_DB_Manager : uses
    QDR_TSS_Download --> QDR_TSS_File_Manager : uses
    QDR_TSS_Cron_Manager --> QDR_TSS_DB_Manager : uses
    QDR_TSS_Cron_Manager --> QDR_TSS_File_Manager : uses
```