fix(compose): mount config.yaml writable so UI can persist changes

The UI mutates /app/config.yaml on every add/remove of subreddits, users
or blacklist entries. With the :ro flag the write fails with OSError and
the route returns 500 (the frontend then shows "Erro de conexão"
because the plain-text 500 body is not JSON-parseable).

Drop :ro from both compose files and from the README volumes table.

docker-compose.yml

@@ -8,7 +8,9 @@ services:
     volumes:
       - ./downloads:/app/downloads
       - ./data:/app/data
-      - ./config.yaml:/app/config.yaml:ro
+      # config.yaml must be writable — the UI mutates it on add/remove of
+      # subreddits, users and blacklist entries.
+      - ./config.yaml:/app/config.yaml
     environment:
       - RMC_TIMEZONE=UTC
       - RMC_DOWNLOAD_DIR=/app/downloads