Migrate internal libs and align project with canonical layout.

Libs:
- lib-utils v0.3.0 → v1.0.0
- lib-aiohttp v0.4.0 → v0.6.0 (request_hook Sequence, attach_apis,
  base_api_lifespan)
- lib-aio-rabbit-broker v2.0.0 → v3.1.0 (MessageQueueBase.message is
  dict[str, Any])
- lib-aiomongo v1.0.1 → v1.1.0 (MongoClientManager shared client)
- lucente-observability v0.6.0 → v0.7.0 (pure-ASGI RequestIdMiddleware)
- lib-auth-guard v0.2.1 (new — replaces local src/guard/index.py)

Architecture:
- attach_apis(app, ...) singleton HTTP clients + base_api_lifespan in
  consumer.py; DI getters Exchange1CApiDep / S3StorageApiDep
- MongoClientManager in lifespan + src/db/ (get_mongo, MongoDep,
  ensure_mongo_indexes)
- partial(_LibAuthGuard, auth_guard_settings) + auth_guard_lifespan in
  AsyncExitStack
- create_technical_auth_hook for outbound JWT (was static
  create_header_temp_token)
- UpdateBackendConsumer canonical: with_log_ctx, Event.RABBIT_CONSUME /
  TASK_SUCCESS / TASK_FAIL, raise NotImplementedError for unknown msg_type
- Pure-ASGI MetricsSecurityMiddleware (template STRICT)
- RabbitMessageQueueBase dropped — MessageQueueBase used directly
- Typed Ctx (HttpCtx/MongoCtx/RabbitCtx/TaskCtx) in merge_ctx;
  Event.APP_START / APP_STOP in lifespan
- LoggingSettings.accessLog field + httpx/httpcore suppress + uvicorn
  access_log= + extra= in gunicorn build_options

Removed:
- src/guard/index.py (local AuthGuard on python-jose)
- src/schemas/auth_model/ (re-imported from lib_auth_guard)
- python-jose, python-json-logger from direct deps (transitive)
- broken health probes (utils_health/redis.py, services.py)

Added:
- tests/ scaffold (35 tests, 72% cov gate awaits)
- .gitlab-ci.yml test stage (python:3.12-slim, junit + cobertura)
- env.template (REQUIRED + OPTIONAL by subsystem)
- CHANGELOG.md (Keep a Changelog)
- src/schemas/{shop,counter}/types.py (ShopBatch / CounterBatch)
- Field(description=...) on bare fields in sale/employee schemas

Verification:
- ruff check src/ app.py consumer.py run_app.py: all checks passed
- poetry check --lock: All set!
- pytest --no-cov: 35 passed
- legacy grep (jose / guard.index / auth_model / lib_utils.security /
  RabbitMessageQueueBase): empty