feat: Universal auto-instrumentation for all languages

## New Features

### Universal Instrumentation Container
- Created deploy/instrumentation/ with Dockerfile that downloads OTel agents for:
  - .NET (glibc and musl/Alpine versions)
  - Node.js (with auto-instrumentation package)
  - Python (bootstrap script + requirements)
  - Java (javaagent JAR)
  - Go (example code for compile-time instrumentation)
  - PHP (composer package + init script)

### Universal instrument.sh Script
- Auto-detects application language from running processes
- Generates docker-compose snippets for each language
- Supports: dotnet, nodejs, python, java, go, php
- Usage: ./instrument.sh <container> [language] [otlp_endpoint]

### Improved docker-compose.yml
- Added instrumentation init container with shared volume
- Added AGENT_KEY environment variable for proper auth
- Added ophion-agent service for host metrics collection
- Named containers for easier management
- Added ophion-network for service discovery

### Documentation
- Created docs/QUICK_START.md with:
  - Single-command installation
  - Instrumentation guide for all languages
  - Troubleshooting section
  - Authentication guide

### Auth Fixes
- Server now properly validates AGENT_KEY for agent authentication
- OTel Collector configured with AGENT_KEY for forwarding to server
- Fixed 401 errors when agents connect

## Files Changed
- docker-compose.yml: Complete stack with all services
- deploy/instrumentation/*: Universal OTel agent container
- deploy/docker/otel-collector-config.yaml: Fixed auth headers
- instrument.sh: Universal instrumentation script
- docs/QUICK_START.md: Complete quick start guide
- README.md: Updated with new features
- .env.example: Added AGENT_KEY

## Testing
- Go code compiles successfully
- Docker images build correctly
- All changes are backwards compatible

deploy/instrumentation/files/nodejs/instrument.js

@@ -0,0 +1,25 @@
+const { NodeSDK } = require('@opentelemetry/sdk-node');
+const { getNodeAutoInstrumentations } = require('@opentelemetry/auto-instrumentations-node');
+const { OTLPTraceExporter } = require('@opentelemetry/exporter-trace-otlp-http');
+const { OTLPMetricExporter } = require('@opentelemetry/exporter-metrics-otlp-http');
+const { PeriodicExportingMetricReader } = require('@opentelemetry/sdk-metrics');
+
+const endpoint = process.env.OTEL_EXPORTER_OTLP_ENDPOINT || 'http://localhost:4318';
+
+const sdk = new NodeSDK({
+  traceExporter: new OTLPTraceExporter({
+    url: endpoint + '/v1/traces',
+  }),
+  metricReader: new PeriodicExportingMetricReader({
+    exporter: new OTLPMetricExporter({
+      url: endpoint + '/v1/metrics',
+    }),
+    exportIntervalMillis: 30000,
+  }),
+  instrumentations: [getNodeAutoInstrumentations()],
+  serviceName: process.env.OTEL_SERVICE_NAME || 'nodejs-app',
+});
+
+sdk.start();
+process.on('SIGTERM', () => sdk.shutdown());
+console.log('[OPHION] OpenTelemetry auto-instrumentation enabled');