fix(api): correct OTEL gRPC endpoint format and SignOz query table

Root cause analysis:
1. OTEL gRPC endpoint had http:// prefix which is invalid for gRPC
2. SignOz query was targeting wrong table (signoz_metrics.distributed_samples_v4)
3. Should query signoz_traces.distributed_signoz_index_v2 for trace data

Fixes:
- Remove http:// prefix from OTEL_EXPORTER_OTLP_ENDPOINT (gRPC needs host:port)
- Update SignOz client to query traces table instead of metrics table
- Fix timestamp format (nanoseconds for DateTime64(9))
- statusCode: 0=Unset, 1=Ok, 2=Error

This should enable OTEL traces to reach SigNoz and GlobalPulse to show real metrics.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/core/config.py

@@ -130,8 +130,8 @@ class Settings(BaseSettings):
         description="Enable OpenTelemetry tracing (disable in MOCK_MODE)",
     )
     OTEL_EXPORTER_OTLP_ENDPOINT: str = Field(
-        default="http://192.168.0.188:24317",
-        description="SigNoz OTLP gRPC endpoint (Host port 24317 -> Container 4317)",
+        default="192.168.0.188:24317",
+        description="SigNoz OTLP gRPC endpoint (Host port 24317 -> Container 4317) - NO http:// prefix for gRPC",
     )
     OTEL_SERVICE_NAME: str = Field(
         default="awoooi-api",