[http_request] Fix infinite loop on read error in update component

The update component had the same infinite loop issue as the OTA component
when network read errors occurred. If container->read() returned an error
(negative value), it would be added to read_index and the loop would continue
indefinitely since get_bytes_read() would never reach content_length.

This fix breaks out of the read loop on any read error (read_bytes <= 0),
preventing watchdog resets and infinite loops during manifest downloads.

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

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

esphome/components/http_request/update/http_request_update.cpp

@@ -76,6 +76,11 @@ void HttpRequestUpdate::update_task(void *params) {
 
     yield();
 
+    if (read_bytes <= 0) {
+      // Network error or connection closed - break to avoid infinite loop
+      break;
+    }
+
     read_index += read_bytes;
   }