Replace custom OTA implementation in web_server_base (#9274)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

tests/component_tests/web_server/test_ota_migration.py

@@ -0,0 +1,38 @@
+"""Tests for web_server OTA migration validation."""
+
+import pytest
+
+from esphome import config_validation as cv
+from esphome.types import ConfigType
+
+
+def test_web_server_ota_true_fails_validation() -> None:
+    """Test that web_server with ota: true fails validation with helpful message."""
+    from esphome.components.web_server import validate_ota_removed
+
+    # Config with ota: true should fail
+    config: ConfigType = {"ota": True}
+
+    with pytest.raises(cv.Invalid) as exc_info:
+        validate_ota_removed(config)
+
+    # Check error message contains migration instructions
+    error_msg = str(exc_info.value)
+    assert "has been removed from 'web_server'" in error_msg
+    assert "platform: web_server" in error_msg
+    assert "ota:" in error_msg
+
+
+def test_web_server_ota_false_passes_validation() -> None:
+    """Test that web_server with ota: false passes validation."""
+    from esphome.components.web_server import validate_ota_removed
+
+    # Config with ota: false should pass
+    config: ConfigType = {"ota": False}
+    result = validate_ota_removed(config)
+    assert result == config
+
+    # Config without ota should also pass
+    config: ConfigType = {}
+    result = validate_ota_removed(config)
+    assert result == config