Silence LongBridge checks and clarify buy note

[Pigbibi]

Summary

Silence successful detection-path notifications for LongBridge while keeping execution reports and logs intact, add the missing /probe endpoint used by Cloud Scheduler, and clarify the buy-skip reason when the target gap is below the minimum one-share order size.

Why

The scheduled /precheck endpoint is intended to detect startup/runtime problems and leave an audit trail, not send a normal successful rebalance notification every morning. Today it still used the real Telegram notification port during validation-only runs, so successful dry-run checks produced user-facing notifications.

The Cloud Scheduler post-open /probe jobs are also configured, but the LongBridge service currently has no /probe route, so those requests return 404 instead of checking broker/account availability.

Separately, buy orders that were skipped because the target allocation gap was smaller than one whole share could be reported as a cash shortage. In the SG example, available cash was enough for one share, but the target gap was intentionally below one-share price, so the message was misleading.

Changes

• Add a silent notification port path for validation-only strategy runs.
• Keep validation-only reports/logging behavior unchanged.
• Add /probe as a dry-run report-scoped broker/account health check.
• Keep successful probe checks silent and notify only when the probe fails.
• Split the buy-skip notification into target-gap-below-one-share vs cash-below-one-share cases.
• Add Chinese and English notification text for the target-gap case.

Validation

• env PYTHONPATH=/home/ubuntu/Projects/QuantPlatformKit/src:/home/ubuntu/Projects/UsEquityStrategies/src python -m pytest tests/test_runtime_composer.py tests/test_request_handling.py::RequestHandlingTests::test_handle_probe_checks_account_snapshot_without_success_notification tests/test_request_handling.py::RequestHandlingTests::test_handle_probe_failure_sends_notification tests/test_request_handling.py::RequestHandlingTests::test_run_strategy_validation_only_uses_dry_run_composer -q
• python -m unittest tests.test_rebalance_service
• python -m py_compile main.py application/runtime_composer.py application/execution_service.py notifications/telegram.py tests/test_runtime_composer.py tests/test_request_handling.py tests/test_rebalance_service.py