Refactor downloader and file manager for improved rclone integration and add healthcheck and smoke test options

- Renamed download flags in ContentDownloader for clarity.
- Enhanced FileManager with methods to build upload paths and verify existing files for rclone uploads.
- Updated StreamProcessor to return success status for stream processing.
- Added rclone smoke test and healthcheck functions to validate configuration and tool availability.
- Improved environment variable handling with a utility function.
- Updated TwitchArchive to incorporate new rclone verification and processing logic.
- Added unit tests for new functionality and refactored existing tests for clarity and coverage.

Co-authored-by: Copilot <copilot@github.com>

docker-compose.override.yml

@@ -0,0 +1,17 @@
+services:
+  twitch-archive:
+    build:
+      context: .
+      dockerfile: docker/python.Dockerfile
+    image: ${TWITCH_ARCHIVE_DEV_IMAGE:-twitch-archive-local}
+    restart: "no"
+    env_file:
+      - ${TWITCH_ARCHIVE_APP_ENV_FILE:-./.env.development}
+    command:
+      - sh
+      - -lc
+      - python twitch-archive.py ${TWITCH_ARCHIVE_ARGS:--u vinesauce --verbose}
+    volumes:
+      - .:/app
+      - ${TWITCH_ARCHIVE_ARCHIVE_BIND:-./archive}:/app/archive
+      - ${TWITCH_ARCHIVE_CONFIG_BIND:-./config}:/app/config