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/http.js

@@ -0,0 +1,80 @@
+/**
+ * HTTP utilities - Fetch helpers and HTTP operations
+ */
+const http = require('http');
+const { TIMEOUTS } = require('../../constants');
+
+/**
+ * Fetch with automatic timeout
+ * Drop-in replacement for fetch() with AbortSignal timeout
+ */
+function fetchT(url, opts = {}, timeoutMs = TIMEOUTS.HTTP_DEFAULT) {
+  // Caddy admin API rejects Node.js undici fetch - use raw http.request
+  if (url.includes(':2019')) {
+    return _httpFetch(url, opts, timeoutMs);
+  }
+  
+  if (!opts.signal) {
+    opts = { ...opts, signal: AbortSignal.timeout(timeoutMs) };
+  }
+  delete opts.timeout;
+  return fetch(url, opts);
+}
+
+/**
+ * Raw http.request wrapper for Caddy admin API
+ */
+function _httpFetch(url, opts = {}, timeoutMs = TIMEOUTS.HTTP_DEFAULT) {
+  return new Promise((resolve, reject) => {
+    const parsed = new URL(url);
+    const options = {
+      hostname: parsed.hostname,
+      port: parsed.port || 2019,
+      path: parsed.pathname + parsed.search,
+      method: (opts.method || 'GET').toUpperCase(),
+      headers: { ...opts.headers },
+      timeout: timeoutMs,
+    };
+    
+    if (opts.body) {
+      options.headers['Content-Length'] = Buffer.byteLength(opts.body);
+    }
+    
+    const MAX_RESPONSE_SIZE = 10 * 1024 * 1024; // 10MB
+    const req = http.request(options, (res) => {
+      let data = '';
+      let size = 0;
+      
+      res.on('data', chunk => {
+        size += chunk.length;
+        if (size > MAX_RESPONSE_SIZE) {
+          res.destroy();
+          reject(new Error(`Response from ${url} exceeded ${MAX_RESPONSE_SIZE} bytes`));
+          return;
+        }
+        data += chunk;
+      });
+      
+      res.on('end', () => {
+        resolve({
+          ok: res.statusCode >= 200 && res.statusCode < 300,
+          status: res.statusCode,
+          statusText: res.statusMessage,
+          json: () => Promise.resolve(JSON.parse(data)),
+          text: () => Promise.resolve(data),
+          headers: { get: (k) => res.headers[k.toLowerCase()] },
+        });
+      });
+    });
+    
+    req.on('timeout', () => {
+      req.destroy();
+      reject(new Error(`Request to ${url} timed out after ${timeoutMs}ms`));
+    });
+    req.on('error', reject);
+    if (opts.body) req.write(opts.body);
+    req.end();
+  });
+}
+
+module.exports = { fetchT };