Implement SimpleNote Web API - full REST API with Express

- Express server with CORS, JSON middleware
- Auth middleware (Bearer token)
- Document CRUD with markdown storage
- Library CRUD with nested support
- Tag indexing and search
- Error handler middleware
- Config from env vars
- Init script for data structure

src/config/index.js

@@ -0,0 +1,27 @@
+/**
+ * SimpleNote Web - Configuration
+ * Environment variables loader with defaults
+ */
+
+import dotenv from 'dotenv';
+import { fileURLToPath } from 'url';
+import { dirname, join, resolve } from 'path';
+import { existsSync } from 'fs';
+
+dotenv.config();
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+const projectRoot = resolve(__dirname, '../..');
+
+export const config = {
+  port: parseInt(process.env.PORT || '3000', 10),
+  host: process.env.HOST || '0.0.0.0',
+  dataRoot: resolve(projectRoot, process.env.DATA_ROOT || './data'),
+  adminToken: process.env.ADMIN_TOKEN || 'snk_initial_admin_token_change_me',
+  logLevel: process.env.LOG_LEVEL || 'info',
+  corsOrigin: process.env.CORS_ORIGIN || '*',
+  apiPrefix: process.env.API_PREFIX || '/api/v1',
+};
+
+export default config;