docs: update documentation to reflect unified config system

- Update config README to focus on current unified system rather than migration
- Update architecture migration doc to reference unifiedConfig instead of appConfig
- Update implementation summary to reference unified.config.ts
- Remove migration-specific content not relevant for new applications
- Provide clear guidance for working with unified configuration system

docs/ARCHITECTURE_MIGRATION.md

@@ -67,14 +67,14 @@ const dbUrl = process.env.VITE_COUCHDB_URL || 'http://localhost:5984';
 #### New Pattern (Recommended)
 
 ```typescript
-import { appConfig, CONFIG } from '../config/app.config';
+import { unifiedConfig } from '../config/unified.config';
 
 // Type-safe, validated configuration
-const baseUrl = appConfig.baseUrl;
-const dbUrl = appConfig.database.url;
+const baseUrl = unifiedConfig.app.baseUrl;
+const dbUrl = unifiedConfig.database.url;
 
-// Or use constants for common values
-const isProduction = CONFIG.IS_PRODUCTION;
+// Or use convenience exports
+const isProduction = unifiedConfig.app.environment === 'production';
 ```
 
 ### Logging Migration
@@ -117,7 +117,7 @@ services/
 │   └── Logger.ts               # Logger implementation
 
 config/                          # ✅ Centralized configuration
-└── app.config.ts               # Main configuration with validation
+└── unified.config.ts           # Main configuration with validation
 ```
 
 ## 🎯 Benefits Achieved