refactor(config): Extract configuration into src/config/ module

- Create src/config/paths.js for all file paths and env vars
- Create src/config/site.js for site configuration loading
- Create src/config/index.js as unified config export
- Prepare for server.js modularization (Phase 2.1)

Part of deslopification roadmap: break 1997-line server.js into layers

dashcaddy-api/src/config/index.js

@@ -0,0 +1,38 @@
+/**
+ * Centralized configuration module
+ * Exports all configuration loading and path resolution
+ */
+const paths = require('./paths');
+const site = require('./site');
+const { APP, LIMITS, TIMEOUTS, RETRIES, CADDY } = require('../../constants');
+
+// Load logging level
+const LOG_LEVELS = { debug: 0, info: 1, warn: 2, error: 3 };
+const LOG_LEVEL = LOG_LEVELS[process.env.LOG_LEVEL || 'info'] || 1;
+
+const PORT = APP.PORT;
+const MAX_ERROR_LOG_SIZE = LIMITS.ERROR_LOG_SIZE;
+
+module.exports = {
+  // Paths
+  ...paths,
+  
+  // Site configuration
+  siteConfig: site.siteConfig,
+  loadSiteConfig: site.loadSiteConfig,
+  buildDomain: site.buildDomain,
+  buildServiceUrl: site.buildServiceUrl,
+  
+  // App constants
+  PORT,
+  LOG_LEVELS,
+  LOG_LEVEL,
+  MAX_ERROR_LOG_SIZE,
+  
+  // Re-export constants for convenience
+  APP,
+  LIMITS,
+  TIMEOUTS,
+  RETRIES,
+  CADDY,
+};