fix(astrolabe): Fix revoke access button HTTP method mismatch

The "Revoke Access" button in Astrolabe personal settings was failing
with "Unable to connect to server" error in multi-user basic auth mode.

Root cause: The JavaScript sends a POST request but the route was
configured to accept DELETE. Changed the route to:
- Use POST method (matching the JavaScript fetch call)
- Use /api/v1/background-sync/credentials/revoke path (avoiding
  conflict with storeAppPassword which uses POST on the base URL)

Added integration test that verifies the complete revoke flow:
enable background sync → click revoke → verify credentials deleted.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -8,6 +8,8 @@ services:
     command: --transaction-isolation=READ-COMMITTED
     volumes:
       - db:/var/lib/mysql
+    ports:
+      - 127.0.0.1:3306:3306
     environment:
       - MYSQL_ROOT_PASSWORD=password
       - MYSQL_PASSWORD=password
@@ -24,7 +26,7 @@ services:
     image: docker.io/library/nextcloud:32.0.3@sha256:53231a9fb9233af2c15bfe70fc03ebe639fd53243fa42a9369884b1e0008deae
     restart: always
     ports:
-      - 0.0.0.0:8080:80
+      - 127.0.0.1:8080:80
     depends_on:
       - redis
       - db