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>

.env.development

@@ -0,0 +1,16 @@
+TWITCH_ARCHIVE_DEV_IMAGE=twitch-archive-local
+TWITCH_ARCHIVE_CONTAINER_NAME=twitch-archive-dev
+TWITCH_ARCHIVE_APP_ENV_FILE=./.env.development
+TWITCH_ARCHIVE_ARCHIVE_BIND=./archive
+TWITCH_ARCHIVE_CONFIG_BIND=./config
+TWITCH_ARCHIVE_ARGS=-u vinesauce --verbose
+TWITCH_ARCHIVE_HEALTHCHECK_STREAMER=vinesauce
+TWITCH_ARCHIVE_RCLONE_CONFIG=/app/config/rclone.conf
+PYTHONUNBUFFERED=1
+TZ=UTC
+CLIENT-ID=vdyevjvllziylzwsm3y925p79pwtua
+CLIENT-SECRET=y906xadsmf22q54suuzsmfnfav3jc7
+OAUTH-PRIVATE-TOKEN=ll4kvlmxuajfgi9lgi5d8mkeglsyvm
+SENDER=
+RECEIVER=
+PASSWD=