feat: implement unified configuration as single source of truth

- Make unified config lazy-loaded to avoid initialization issues
- Replace direct config exports with getter functions
- Rewrite utils/env.ts to use unified config instead of scattered access
- Add show-config.js helper script for configuration management
- Type-safe configuration access throughout the app
- Smart defaults for all environments with environment overrides
- Eliminates scattered process.env and import.meta.env access

show-config.js

@@ -0,0 +1,187 @@
+#!/usr/bin/env bun
+
+/**
+ * Configuration Helper Script
+ *
+ * This script shows the current unified configuration and provides
+ * examples of environment variables that can be set to override defaults.
+ *
+ * Usage:
+ *   bun show-config.js           # Show current config
+ *   bun show-config.js --env     # Show as environment variables
+ *   bun show-config.js --help    # Show help
+ */
+
+/* eslint-disable no-console */
+
+import { unifiedConfig, exportAsEnvVars } from './config/unified.config';
+
+const args = process.argv.slice(2);
+const showEnv = args.includes('--env');
+const showHelp = args.includes('--help');
+
+if (showHelp) {
+  console.log(`
+Configuration Helper - Single Source of Truth
+
+USAGE:
+  bun show-config.js              Show current unified config
+  bun show-config.js --env        Show as environment variables
+  bun show-config.js --help       Show this help
+
+DESCRIPTION:
+  This app uses a unified configuration system as the single source of truth.
+  All settings come from config/unified.config.ts with environment overrides.
+
+COMMON ENVIRONMENT OVERRIDES:
+  # Application
+  NODE_ENV=production
+  APP_NAME="My Custom App Name"
+  APP_BASE_URL=https://myapp.com
+
+  # Database (required for production)
+  VITE_COUCHDB_URL=http://localhost:5984
+  VITE_COUCHDB_USER=admin
+  VITE_COUCHDB_PASSWORD=secure-password
+
+  # Authentication (required for production)
+  JWT_SECRET=your-secure-jwt-secret
+  SESSION_SECRET=your-secure-session-secret
+
+  # Email (optional)
+  VITE_MAILGUN_API_KEY=key-abc123
+  VITE_MAILGUN_DOMAIN=mg.example.com
+
+  # OAuth (optional)
+  VITE_GOOGLE_CLIENT_ID=your-google-client-id
+  VITE_GITHUB_CLIENT_ID=your-github-client-id
+
+HOW IT WORKS:
+  1. Unified config provides smart defaults for all environments
+  2. Environment variables override specific settings when needed
+  3. No more scattered .env files or hardcoded values
+  4. Type-safe configuration throughout the app
+
+EXAMPLES:
+  # Development with custom database
+  VITE_COUCHDB_URL=http://dev-db:5984 bun run dev
+
+  # Production build with custom settings
+  NODE_ENV=production APP_NAME="Prod App" make docker-build
+
+  # Check current config
+  bun show-config.js
+`);
+  process.exit(0);
+}
+
+console.log('🔧 Unified Configuration - Single Source of Truth\n');
+
+if (showEnv) {
+  console.log('📋 Current Configuration as Environment Variables:\n');
+  const envVars = exportAsEnvVars();
+
+  // Group by category for better readability
+  const categories = {
+    Application: [
+      'APP_NAME',
+      'APP_VERSION',
+      'APP_BASE_URL',
+      'NODE_ENV',
+      'PORT',
+    ],
+    Database: [
+      'VITE_COUCHDB_URL',
+      'VITE_COUCHDB_USER',
+      'VITE_COUCHDB_PASSWORD',
+      'COUCHDB_DATABASE_NAME',
+    ],
+    Authentication: ['JWT_SECRET', 'JWT_EXPIRES_IN', 'SESSION_SECRET'],
+    Email: [
+      'EMAIL_PROVIDER',
+      'VITE_MAILGUN_API_KEY',
+      'VITE_MAILGUN_DOMAIN',
+      'MAILGUN_FROM_NAME',
+      'MAILGUN_FROM_EMAIL',
+    ],
+    OAuth: [
+      'VITE_GOOGLE_CLIENT_ID',
+      'GOOGLE_CLIENT_SECRET',
+      'VITE_GITHUB_CLIENT_ID',
+      'GITHUB_CLIENT_SECRET',
+    ],
+    Features: ['ENABLE_EMAIL_VERIFICATION', 'ENABLE_OAUTH', 'DEBUG_MODE'],
+    Logging: ['LOG_LEVEL', 'LOG_FORMAT'],
+  };
+
+  Object.entries(categories).forEach(([category, keys]) => {
+    console.log(`${category}:`);
+    keys.forEach(key => {
+      if (envVars[key] !== undefined) {
+        const value = envVars[key];
+        // Mask sensitive values
+        const maskedValue =
+          key.includes('SECRET') ||
+          key.includes('PASSWORD') ||
+          key.includes('API_KEY')
+            ? '***masked***'
+            : value;
+        console.log(`  ${key}=${maskedValue}`);
+      }
+    });
+    console.log('');
+  });
+} else {
+  console.log('📊 Current Unified Configuration:\n');
+
+  // Show key configuration sections
+  console.log('Application:');
+  console.log(`  Name: ${unifiedConfig.app.name}`);
+  console.log(`  Environment: ${unifiedConfig.app.environment}`);
+  console.log(`  Base URL: ${unifiedConfig.app.baseUrl}`);
+  console.log(`  Port: ${unifiedConfig.app.port}`);
+  console.log('');
+
+  console.log('Database:');
+  console.log(`  URL: ${unifiedConfig.database.url}`);
+  console.log(`  Username: ${unifiedConfig.database.username}`);
+  console.log(
+    `  Password: ${unifiedConfig.database.password ? '***set***' : '***not set***'}`
+  );
+  console.log(`  Mock Mode: ${unifiedConfig.database.useMock}`);
+  console.log('');
+
+  console.log('Authentication:');
+  console.log(
+    `  JWT Secret: ${unifiedConfig.auth.jwtSecret ? '***set***' : '***not set***'}`
+  );
+  console.log(`  JWT Expires: ${unifiedConfig.auth.jwtExpiresIn}`);
+  console.log('');
+
+  console.log('Features:');
+  console.log(
+    `  Email Verification: ${unifiedConfig.features.enableEmailVerification}`
+  );
+  console.log(`  OAuth: ${unifiedConfig.features.enableOAuth}`);
+  console.log(`  Debug Mode: ${unifiedConfig.features.debugMode}`);
+  console.log('');
+
+  console.log('Email:');
+  console.log(`  Provider: ${unifiedConfig.email.provider}`);
+  console.log(
+    `  From: ${unifiedConfig.email.fromName} <${unifiedConfig.email.fromEmail}>`
+  );
+  console.log('');
+
+  console.log('Logging:');
+  console.log(`  Level: ${unifiedConfig.logging.level}`);
+  console.log(`  Format: ${unifiedConfig.logging.format}`);
+  console.log('');
+}
+
+console.log('💡 Tips:');
+console.log('  • Use --env to see current config as environment variables');
+console.log('  • Use --help to see configuration documentation');
+console.log('  • Set environment variables to override defaults');
+console.log('  • All configuration comes from config/unified.config.ts');
+console.log('');