Fix VISIT button showing for devices without web_server configured

[bdraco]

Summary

Fixes an issue where the VISIT button incorrectly appears for devices that don't have the web_server component configured, due to loaded_integrations including web_server when components like captive_portal are enabled.

Problem

When a device configuration includes captive_portal:

1. The captive portal component auto-loads the ota.web_server platform for its OTA functionality
2. ESPHome's loaded_integrations in the storage JSON includes web_server even though the user never explicitly configured it
3. The dashboard was checking loaded_integrations to determine whether to show the VISIT button
4. Result: VISIT button appears but leads to a non-functional web server (404 error)

This affects all devices compiled with ESPHome 2025.7+ that have captive_portal enabled but no explicit web_server configuration.

Solution

Changed the VISIT button visibility logic to check the web_port field instead of the loaded_integrations array.

The web_port property in ESPHome core (esphome/core/__init__.py:652-662) checks CONF_WEB_SERVER in self.config rather than relying on integration loading state. This is the source of truth for explicit user configuration:

• web_port: 80 (or other port number) = web server is explicitly configured by user
• web_port: null = no web server configured (even if web_server appears in loaded_integrations)

This provides a reliable indicator of whether the device has an accessible web interface.

Unit tests were added in esphome/esphome#11811 to prevent regression of the web_port property behavior.

Changes

• src/devices/configured-device-card.ts:120: Changed condition from this.device.loaded_integrations?.includes("web_server") to this.device.web_port != null