feat: allow a docs directory coming from env

Current config assumes /data/docs to be part of the current data directory.

This allows DOCS_DIR to be mounted from a different path outside of DATA_DIR, or falls back to the previous behaviour if DOCS_DIR is not in the environment

backend/config.py

@@ -162,7 +162,7 @@ Path(CACHE_DIR).mkdir(parents=True, exist_ok=True)
 # Docs DIR
 ####################################
 
-DOCS_DIR = f"{DATA_DIR}/docs"
+DOCS_DIR = os.getenv("DOCS_DIR", f"{DATA_DIR}/docs")
 Path(DOCS_DIR).mkdir(parents=True, exist_ok=True)