refactor(utils): Extract utilities from server.js

- Create src/utils/http.js - fetchT and HTTP helpers
- Create src/utils/logging.js - Structured logging and error logging
- Create src/utils/responses.js - Standard API responses
- Create src/utils/async-handler.js - Async wrapper with error handling
- Create src/utils/index.js - Consolidated exports

Removes scattered helper functions from server.js

dashcaddy-api/src/utils/logging.js

@@ -0,0 +1,119 @@
+/**
+ * Logging utilities - Structured logging and error handling
+ */
+const fsp = require('fs').promises;
+const path = require('path');
+
+const LOG_LEVELS = { debug: 0, info: 1, warn: 2, error: 3 };
+
+/**
+ * Create a structured logger
+ */
+function createLogger(LOG_LEVEL) {
+  function log(level, context, message, data = {}) {
+    if (LOG_LEVELS[level] < LOG_LEVEL) return;
+    
+    const entry = {
+      t: new Date().toISOString(),
+      level,
+      ctx: context,
+      msg: message,
+    };
+    
+    if (Object.keys(data).length) entry.data = data;
+    
+    const fn = level === 'error' ? console.error : level === 'warn' ? console.warn : console.info;
+    fn(JSON.stringify(entry));
+  }
+  
+  log.info = (ctx, msg, data) => log('info', ctx, msg, data);
+  log.warn = (ctx, msg, data) => log('warn', ctx, msg, data);
+  log.error = (ctx, msg, data) => log('error', ctx, msg, data);
+  log.debug = (ctx, msg, data) => log('debug', ctx, msg, data);
+  
+  return log;
+}
+
+/**
+ * Enhanced error logging with context tracking
+ */
+async function logError(ERROR_LOG_FILE, MAX_ERROR_LOG_SIZE, context, error, additionalInfo = {}, log) {
+  const timestamp = new Date().toISOString();
+
+  // Extract request context
+  const requestContext = {};
+  if (additionalInfo.req) {
+    const req = additionalInfo.req;
+    const clientIP = req.ip || req.socket?.remoteAddress || '';
+    requestContext.requestId = req.id;
+    requestContext.ip = clientIP;
+    requestContext.userAgent = req.get('user-agent');
+    requestContext.method = req.method;
+    requestContext.path = req.path;
+    delete additionalInfo.req;
+  }
+
+  const logEntry = {
+    timestamp,
+    context,
+    ...requestContext,
+    error: {
+      message: error.message || error,
+      stack: error.stack,
+      code: error.code
+    },
+    ...additionalInfo
+  };
+
+  const contextInfo = Object.keys(requestContext).length > 0
+    ? `\nRequest Context: ${JSON.stringify(requestContext, null, 2)}`
+    : '';
+  const logLine = `[${timestamp}] ${context}: ${error.message || error}\n${error.stack || ''}${contextInfo}\nAdditional Info: ${JSON.stringify(additionalInfo, null, 2)}\n${'='.repeat(80)}\n`;
+
+  try {
+    // Rotate log if it exceeds max size
+    try {
+      const stats = await fsp.stat(ERROR_LOG_FILE);
+      if (stats.size > MAX_ERROR_LOG_SIZE) {
+        const rotated = ERROR_LOG_FILE + '.1';
+        const exists = await fsp.access(rotated).then(() => true).catch(() => false);
+        if (exists) await fsp.unlink(rotated);
+        await fsp.rename(ERROR_LOG_FILE, rotated);
+      }
+    } catch (_) { /* file may not exist yet */ }
+    
+    await fsp.appendFile(ERROR_LOG_FILE, logLine);
+  } catch (e) {
+    if (log && log.error) {
+      log.error('errorlog', 'Failed to write to error log', { error: e.message });
+    }
+  }
+}
+
+/**
+ * Return a safe error message without leaking internals
+ */
+function safeErrorMessage(error) {
+  const msg = error.message || String(error);
+
+  // Detect port conflict errors
+  const portMatch = msg.match(/exposing port TCP [^:]*:(\d+)/);
+  if (portMatch || msg.includes('port is already allocated') || msg.includes('ports are not available')) {
+    const port = portMatch ? portMatch[1] : 'requested';
+    return `[DC-200] Port ${port} is already in use. Try a different port or stop the service using that port first.`;
+  }
+
+  // Only expose short, user-facing messages
+  if (msg.length < 200 && !msg.includes('/') && !msg.includes('\\') && !msg.includes(' at ')) {
+    return msg;
+  }
+  
+  return 'An internal error occurred';
+}
+
+module.exports = {
+  LOG_LEVELS,
+  createLogger,
+  logError,
+  safeErrorMessage,
+};