fix(antidetect): Match browser timezone to proxy IP location

- Add IP geolocation lookup via ip-api.com to get timezone from proxy IP
- Use ipify.org API for reliable proxy IP detection (replaces unreliable fingerprint.com scraping)
- Set browser timezone via CDP Emulation.setTimezoneOverride to match proxy location
- Add detectedTimezone and detectedLocation to preflight result
- Add /api/worker-registry/preflight-test endpoint for smoke testing

Fixes timezone mismatch where browser showed America/Phoenix while proxy was in America/New_York

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/services/puppeteer-preflight.ts

@@ -26,6 +26,34 @@ const TEST_PLATFORM_ID = '6405ef617056e8014d79101b';
 const FINGERPRINT_DEMO_URL = 'https://demo.fingerprint.com/';
 const AMIUNIQUE_URL = 'https://amiunique.org/fingerprint';
 
+// IP geolocation API for timezone lookup (free, no key required)
+const IP_API_URL = 'http://ip-api.com/json';
+
+/**
+ * Look up timezone from IP address using ip-api.com
+ * Returns IANA timezone (e.g., 'America/New_York') or null on failure
+ */
+async function getTimezoneFromIp(ip: string): Promise<{ timezone: string; city?: string; region?: string } | null> {
+  try {
+    const axios = require('axios');
+    const response = await axios.get(`${IP_API_URL}/${ip}?fields=status,timezone,city,regionName`, {
+      timeout: 5000,
+    });
+
+    if (response.data?.status === 'success' && response.data?.timezone) {
+      return {
+        timezone: response.data.timezone,
+        city: response.data.city,
+        region: response.data.regionName,
+      };
+    }
+    return null;
+  } catch (err: any) {
+    console.log(`[PuppeteerPreflight] IP geolocation lookup failed: ${err.message}`);
+    return null;
+  }
+}
+
 export interface PuppeteerPreflightResult extends PreflightResult {
   method: 'http';
   /** Number of products returned (proves API access) */
@@ -42,6 +70,13 @@ export interface PuppeteerPreflightResult extends PreflightResult {
   expectedProxyIp?: string;
   /** Whether IP verification passed (detected IP matches proxy) */
   ipVerified?: boolean;
+  /** Detected timezone from IP geolocation */
+  detectedTimezone?: string;
+  /** Detected location from IP geolocation */
+  detectedLocation?: {
+    city?: string;
+    region?: string;
+  };
 }
 
 /**
@@ -136,7 +171,52 @@ export async function runPuppeteerPreflight(
     };
 
     // =========================================================================
-    // STEP 1: Visit fingerprint.com demo to verify anti-detect and get IP
+    // STEP 1a: Get IP address directly via simple API (more reliable than scraping)
+    // =========================================================================
+    console.log(`[PuppeteerPreflight] Getting proxy IP address...`);
+    try {
+      const ipApiResponse = await page.evaluate(async () => {
+        try {
+          const response = await fetch('https://api.ipify.org?format=json');
+          const data = await response.json();
+          return { ip: data.ip, error: null };
+        } catch (err: any) {
+          return { ip: null, error: err.message };
+        }
+      });
+
+      if (ipApiResponse.ip) {
+        result.proxyIp = ipApiResponse.ip;
+        result.proxyConnected = true;
+        console.log(`[PuppeteerPreflight] Detected proxy IP: ${ipApiResponse.ip}`);
+
+        // Look up timezone from IP
+        const geoData = await getTimezoneFromIp(ipApiResponse.ip);
+        if (geoData) {
+          result.detectedTimezone = geoData.timezone;
+          result.detectedLocation = { city: geoData.city, region: geoData.region };
+          console.log(`[PuppeteerPreflight] IP Geolocation: ${geoData.city}, ${geoData.region} (${geoData.timezone})`);
+
+          // Set browser timezone to match proxy location via CDP
+          try {
+            const client = await page.target().createCDPSession();
+            await client.send('Emulation.setTimezoneOverride', { timezoneId: geoData.timezone });
+            console.log(`[PuppeteerPreflight] Browser timezone set to: ${geoData.timezone}`);
+          } catch (tzErr: any) {
+            console.log(`[PuppeteerPreflight] Failed to set browser timezone: ${tzErr.message}`);
+          }
+        } else {
+          console.log(`[PuppeteerPreflight] WARNING: Could not determine timezone from IP - timezone mismatch possible`);
+        }
+      } else {
+        console.log(`[PuppeteerPreflight] IP lookup failed: ${ipApiResponse.error || 'unknown error'}`);
+      }
+    } catch (ipErr: any) {
+      console.log(`[PuppeteerPreflight] IP API error: ${ipErr.message}`);
+    }
+
+    // =========================================================================
+    // STEP 1b: Visit fingerprint.com demo to verify anti-detect
     // =========================================================================
     console.log(`[PuppeteerPreflight] Testing anti-detect at ${FINGERPRINT_DEMO_URL}...`);
 
@@ -199,6 +279,8 @@ export async function runPuppeteerPreflight(
             // Don't fail - residential proxies often show different egress IPs
           }
         }
+
+        // Note: Timezone already set earlier via ipify.org IP lookup
       }
 
       if (fingerprintData.visitorId) {