chore: remainder — backend test infra, agent config, docker, i18n, frontend ui

- Backend: alembic env, config manager/models, dependencies, translate plugin
- Backend tests: async_sync_regression, integration tests, git services, test_agent
- Docker: docker-compose.yml updates
- Agent: qa-tester.md update, semantics-testing SKILL.md update
- Frontend: TopNavbar, sidebarNavigation, FeaturesSettings, FeatureGate
- i18n: assistant.json en/ru locale updates
- New: frontend/src/lib/components/agent/ directory

docker-compose.yml

@@ -44,6 +44,28 @@ services:
     volumes:
       - ./storage:/app/storage
 
+  agent:
+    build:
+      context: .
+      dockerfile: docker/Dockerfile.agent
+    restart: unless-stopped
+    depends_on:
+      db:
+        condition: service_healthy
+      backend:
+        condition: service_started
+    environment:
+      LLM_API_KEY: ${LLM_API_KEY:-}
+      LLM_BASE_URL: ${LLM_BASE_URL:-https://api.openai.com/v1}
+      LLM_MODEL: ${LLM_MODEL:-gpt-4o}
+      FASTAPI_URL: http://backend:8000
+      JWT_SECRET: ${JWT_SECRET:-super-secret-key}
+      SERVICE_TOKEN_SECRET: ${SERVICE_TOKEN_SECRET:-agent-service-secret}
+      DATABASE_URL: postgresql+psycopg2://postgres:postgres@db:5432/ss_tools
+      GRADIO_SERVER_PORT: 7860
+    ports:
+      - "7860"  # internal only, proxied through nginx
+
   frontend:
     build:
       context: .