feat: Add OpenTelemetry OTLP HTTP receiver

- Add POST /v1/traces endpoint for OTLP JSON trace ingestion
- Convert OTLP spans to internal format and save to PostgreSQL
- Manual JSON parsing (no Go 1.24 dependencies)
- Add Node.js instrumentation example with Express
- Add Python instrumentation example with Flask
- Auto-instrumentation support for both languages

examples/otel-nodejs/README.md

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+# Node.js OpenTelemetry Example for Ophion
+
+This example demonstrates how to instrument a Node.js application with OpenTelemetry and send traces to Ophion.
+
+## Setup
+
+```bash
+# Install dependencies
+npm install
+
+# Start Ophion server (in another terminal)
+# cd ~/projetos_jarvis/ophion && go run cmd/server/main.go
+
+# Run the app with tracing
+npm run trace
+```
+
+## Environment Variables
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `OTEL_EXPORTER_OTLP_ENDPOINT` | `http://localhost:8080/v1/traces` | Ophion OTLP endpoint |
+| `OTEL_SERVICE_NAME` | `nodejs-example` | Service name in traces |
+| `PORT` | `3000` | App HTTP port |
+
+## Test Endpoints
+
+```bash
+# Health check
+curl http://localhost:3000/health
+
+# Get all users (generates trace)
+curl http://localhost:3000/users
+
+# Get single user
+curl http://localhost:3000/users/1
+
+# Create order (complex trace with nested spans)
+curl -X POST http://localhost:3000/orders \
+  -H "Content-Type: application/json" \
+  -d '{"items": [{"id": 1, "qty": 2}]}'
+
+# Trigger error (error trace)
+curl http://localhost:3000/error
+```
+
+## View Traces in Ophion
+
+```bash
+# List recent traces
+curl http://localhost:8080/api/v1/traces
+
+# Get specific trace
+curl http://localhost:8080/api/v1/traces/<trace_id>
+```
+
+## How It Works
+
+1. `tracing.js` - Initializes OpenTelemetry SDK with OTLP HTTP exporter
+2. Auto-instrumentation captures HTTP requests automatically
+3. Manual spans in `app.js` add custom business logic traces
+4. All spans are sent to Ophion's `/v1/traces` endpoint in OTLP JSON format