chore: bind-mount docker volumes under the repo (./volumes), gitignore them

Replace the named volumes mongo-data and work-data with bind mounts to
./volumes/mongo and ./volumes/work so all runtime state lives under the repo
tree. Existing data was migrated; the old named volumes were removed. The
${HOME}/.claude host-credential mounts are intentionally left as-is (must not
live in the repo). Added /volumes/ to .gitignore.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docker-compose.yml

@@ -13,7 +13,8 @@ services:
     # Mongo is reachable only on the compose network; never published to the
     # host (§12).
     volumes:
-      - mongo-data:/data/db
+      # data lives in-repo (gitignored) so all state is under one tree
+      - ./volumes/mongo:/data/db
     healthcheck:
       test: ["CMD", "mongosh", "--quiet", "--eval", "db.adminCommand('ping').ok"]
       interval: 10s
@@ -82,7 +83,7 @@ services:
     volumes:
       - ${HOME}/.claude:/home/node/.claude
       - ${HOME}/.claude.json:/home/node/.claude.json
-      - work-data:/work
+      - ./volumes/work:/work
     ports:
       - "127.0.0.1:8091:8091"
     extra_hosts:
@@ -93,7 +94,3 @@ services:
       timeout: 5s
       retries: 3
       start_period: 5s
-
-volumes:
-  mongo-data:
-  work-data: