feat: add comprehensive environment variable parsing with nested resolution and hardcoded variable detection

This commit introduces advanced environment variable handling capabilities including:
- Nested environment variable resolution with circular dependency detection
- Extraction of hardcoded environment variables from docker-compose.yml
- New ShowHardcoded Livewire component for displaying detected variables
- Enhanced UI for better environment variable management

The changes improve the user experience by automatically detecting and displaying
environment variables that are hardcoded in docker-compose files, allowing users
to override them if needed. The nested variable resolution ensures complex variable
dependencies are properly handled.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/Unit/ExtractHardcodedEnvironmentVariablesTest.php

@@ -0,0 +1,147 @@
+<?php
+
+test('extracts simple environment variables from docker-compose', function () {
+    $yaml = <<<'YAML'
+services:
+  app:
+    image: nginx
+    environment:
+      - NODE_ENV=production
+      - PORT=3000
+YAML;
+
+    $result = extractHardcodedEnvironmentVariables($yaml);
+
+    expect($result)->toHaveCount(2)
+        ->and($result[0]['key'])->toBe('NODE_ENV')
+        ->and($result[0]['value'])->toBe('production')
+        ->and($result[0]['service_name'])->toBe('app')
+        ->and($result[1]['key'])->toBe('PORT')
+        ->and($result[1]['value'])->toBe('3000')
+        ->and($result[1]['service_name'])->toBe('app');
+});
+
+test('extracts environment variables with inline comments', function () {
+    $yaml = <<<'YAML'
+services:
+  app:
+    environment:
+      - NODE_ENV=production  # Production environment
+      - DEBUG=false  # Disable debug mode
+YAML;
+
+    $result = extractHardcodedEnvironmentVariables($yaml);
+
+    expect($result)->toHaveCount(2)
+        ->and($result[0]['comment'])->toBe('Production environment')
+        ->and($result[1]['comment'])->toBe('Disable debug mode');
+});
+
+test('handles multiple services', function () {
+    $yaml = <<<'YAML'
+services:
+  app:
+    environment:
+      - APP_ENV=prod
+  db:
+    environment:
+      - POSTGRES_DB=mydb
+YAML;
+
+    $result = extractHardcodedEnvironmentVariables($yaml);
+
+    expect($result)->toHaveCount(2)
+        ->and($result[0]['key'])->toBe('APP_ENV')
+        ->and($result[0]['service_name'])->toBe('app')
+        ->and($result[1]['key'])->toBe('POSTGRES_DB')
+        ->and($result[1]['service_name'])->toBe('db');
+});
+
+test('handles associative array format', function () {
+    $yaml = <<<'YAML'
+services:
+  app:
+    environment:
+      NODE_ENV: production
+      PORT: 3000
+YAML;
+
+    $result = extractHardcodedEnvironmentVariables($yaml);
+
+    expect($result)->toHaveCount(2)
+        ->and($result[0]['key'])->toBe('NODE_ENV')
+        ->and($result[0]['value'])->toBe('production')
+        ->and($result[1]['key'])->toBe('PORT')
+        ->and($result[1]['value'])->toBe(3000); // Integer values stay as integers from YAML
+});
+
+test('handles environment variables without values', function () {
+    $yaml = <<<'YAML'
+services:
+  app:
+    environment:
+      - API_KEY
+      - DEBUG=false
+YAML;
+
+    $result = extractHardcodedEnvironmentVariables($yaml);
+
+    expect($result)->toHaveCount(2)
+        ->and($result[0]['key'])->toBe('API_KEY')
+        ->and($result[0]['value'])->toBe('') // Variables without values get empty string, not null
+        ->and($result[1]['key'])->toBe('DEBUG')
+        ->and($result[1]['value'])->toBe('false');
+});
+
+test('returns empty collection for malformed YAML', function () {
+    $yaml = 'invalid: yaml: content::: [[[';
+
+    $result = extractHardcodedEnvironmentVariables($yaml);
+
+    expect($result)->toBeEmpty();
+});
+
+test('returns empty collection for empty compose file', function () {
+    $result = extractHardcodedEnvironmentVariables('');
+
+    expect($result)->toBeEmpty();
+});
+
+test('returns empty collection when no services defined', function () {
+    $yaml = <<<'YAML'
+version: '3.8'
+networks:
+  default:
+YAML;
+
+    $result = extractHardcodedEnvironmentVariables($yaml);
+
+    expect($result)->toBeEmpty();
+});
+
+test('returns empty collection when service has no environment section', function () {
+    $yaml = <<<'YAML'
+services:
+  app:
+    image: nginx
+YAML;
+
+    $result = extractHardcodedEnvironmentVariables($yaml);
+
+    expect($result)->toBeEmpty();
+});
+
+test('handles mixed associative and array format', function () {
+    $yaml = <<<'YAML'
+services:
+  app:
+    environment:
+      - NODE_ENV=production
+      PORT: 3000
+YAML;
+
+    $result = extractHardcodedEnvironmentVariables($yaml);
+
+    // Mixed format is invalid YAML and returns empty collection
+    expect($result)->toBeEmpty();
+});