**Problem**:
- api_gateway binary and real_backend_integration_test had compilation errors
- Missing observability module caused binary to fail compilation
- Incorrect proto imports and field access in integration tests
**Changes**:
1. services/api_gateway/src/main.rs:
- Removed call to common::observability::init_observability (module commented out in common)
- Replaced with simple tracing_subscriber::fmt::init()
- Removed unused imports (layer::SubscriberExt, util::SubscriberInitExt)
2. services/api_gateway/tests/real_backend_integration_test.rs:
- Fixed proto imports: use tli::proto::health::{HealthClient, HealthCheckRequest}
- Replaced TradingServiceClient with HealthClient (standard gRPC health check)
- Replaced BacktestingServiceClient with HealthClient
- Fixed field access: health.status -> health.healthy for ML service
- Fixed field access: health.status string -> health.status i32 (ServingStatus enum)
- Updated all 8 test functions to use correct proto types
- Pre-commit hook automatically changed .health_check() to .check() (correct method name)
**Tests Fixed**:
- api_gateway binary compilation (1 error fixed)
- real_backend_integration_test compilation (7 errors fixed)
**Impact**:
- 2 of 6 service test failures resolved
- api_gateway binary now compiles and runs
- Integration tests now use correct proto definitions
Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
