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/php/otel_init.php

@@ -0,0 +1,29 @@
+<?php
+/**
+ * OPHION PHP OpenTelemetry Initialization
+ * Include this file in your application bootstrap
+ */
+
+use OpenTelemetry\SDK\Sdk;
+use OpenTelemetry\SDK\Trace\TracerProvider;
+use OpenTelemetry\SDK\Trace\SpanProcessor\SimpleSpanProcessor;
+use OpenTelemetry\Contrib\Otlp\SpanExporter;
+use OpenTelemetry\SDK\Common\Export\Http\PsrTransportFactory;
+use OpenTelemetry\SDK\Resource\ResourceInfo;
+use OpenTelemetry\SDK\Common\Attribute\Attributes;
+
+$endpoint = getenv('OTEL_EXPORTER_OTLP_ENDPOINT') ?: 'http://localhost:4318';
+$serviceName = getenv('OTEL_SERVICE_NAME') ?: 'php-app';
+
+try {
+    $transport = (new PsrTransportFactory())->create($endpoint . '/v1/traces', 'application/json');
+    $exporter = new SpanExporter($transport);
+    $tracerProvider = TracerProvider::builder()
+        ->addSpanProcessor(new SimpleSpanProcessor($exporter))
+        ->setResource(ResourceInfo::create(Attributes::create(['service.name' => $serviceName])))
+        ->build();
+    Sdk::builder()->setTracerProvider($tracerProvider)->buildAndRegisterGlobal();
+    error_log('[OPHION] OpenTelemetry initialized for PHP');
+} catch (Exception $e) {
+    error_log('[OPHION] Failed to initialize OpenTelemetry: ' . $e->getMessage());
+}