Add E2E tests, fix bugs

Made-with: Cursor

_docs/02_document/deployment/observability.md

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+# Observability
+
+## Logging
+
+**Library**: Loguru 0.7.3
+
+**Sinks**:
+
+| Sink   | Level   | Filter                             | Destination                          |
+|--------|---------|-------------------------------------|--------------------------------------|
+| File   | INFO+   | All                                 | `Logs/log_loader_{YYYYMMDD}.txt`     |
+| Stdout | DEBUG   | INFO, DEBUG, SUCCESS only           | Container stdout                     |
+| Stderr | WARNING+| All                                 | Container stderr                     |
+
+**Format**: `[HH:mm:ss LEVEL] message`
+
+**Rotation**: Daily (1 day), 30-day retention (file sink only)
+
+**Async**: File sink uses `enqueue=True` for non-blocking writes
+
+## Health Checks
+
+| Endpoint     | Method | Response           | Purpose         |
+|-------------|--------|--------------------|------------------|
+| `/health`   | GET    | `{"status": "healthy"}` | Liveness probe  |
+| `/status`   | GET    | `{status, authenticated, modelCacheDir}` | Readiness/info |
+
+## Metrics
+
+No metrics collection (Prometheus, StatsD, etc.) is implemented.
+
+## Tracing
+
+No distributed tracing is implemented.
+
+## Gaps
+
+- No structured logging (JSON format) — plain text only
+- No request-level logging middleware (request ID, duration, status code)
+- No metrics endpoint
+- No distributed tracing
+- Log directory `Logs/` is hardcoded — not configurable via environment