Add output cleanup policy

README.md

@@ -91,6 +91,9 @@ Compose settings are stored in `env`. Update that file to change values such as:
 - `SECRET_KEY`
 - `MAX_UPLOAD_SIZE_MB`
 - `OUTPUT_DIRECTORY`
+- `OUTPUT_RETENTION_HOURS`
+- `CLEANUP_ON_STARTUP`
+- `CLEANUP_AFTER_DOWNLOAD`
 
 ### Run the test suite in a container
 
@@ -126,6 +129,7 @@ curl -X POST http://127.0.0.1:5000/convert \
 ## Notes
 
 - Temporary output files are written to `instance/outputs`
+- Generated files are cleaned up according to the configured output retention policy
 - The application does not require a database
 - Gunicorn is used as the production WSGI server
 - Parsing and export writing are streamed to reduce memory usage on large uploads
@@ -133,3 +137,6 @@ curl -X POST http://127.0.0.1:5000/convert \
 - Default upload limit is 100 MiB
 - Set `MAX_UPLOAD_SIZE_MB` to configure the upload limit in megabytes
 - `MAX_CONTENT_LENGTH` is also supported as a lower-level byte-based override
+- `OUTPUT_RETENTION_HOURS` controls how long generated output files are kept
+- `CLEANUP_ON_STARTUP=true` removes expired generated files when the app starts
+- `CLEANUP_AFTER_DOWNLOAD=true` deletes a result only after the response finishes sending