docs: add environment variables section to existing advanced page

Per reviewer feedback, instead of creating a new page, add the operator
environment variables documentation as a section in the existing
fine-tuning page (advanced.adoc).

Author: bimakw

docs/modules/ROOT/nav.adoc

@@ -20,7 +20,6 @@
 *** xref:installation/advanced/http-proxy.adoc[HTTP Proxy]
 *** xref:installation/advanced/offline.adoc[Offline]
 *** xref:installation/advanced/pruning-registry.adoc[Pruning Registry]
-*** xref:installation/advanced/operator-tuning.adoc[Operator Tuning]
 * xref:running/running.adoc[Run an Integration]
 ** xref:running/running-cli.adoc[kamel run CLI]
 ** xref:running/build-from-git.adoc[Git hosted Integrations]

docs/modules/ROOT/pages/installation/advanced/advanced.adoc

@@ -34,3 +34,44 @@ The service exposed on the _/metrics_ endpoint is compatible with Prometheus. Yo
 == Logging
 
 By default, the operator Pod logging level is set to INFO. You may require to change this value to log also DEBUG. In this case you need to provide an environment variable to the operator Deployment, _LOG_LEVEL_ which can be set to `debug`. You can also lower the number of logging tracing by setting this value to `error` (advisable for production environments).
+
+== Environment Variables
+
+The following environment variables can be configured on the operator Deployment to tune the operator behavior:
+
+[cols="2,1,3"]
+|===
+|Variable |Default |Description
+
+|`WATCH_NAMESPACE`
+|_empty_
+|The namespace(s) the operator watches for Integration resources. When not set or empty, the operator watches all namespaces.
+
+|`NAMESPACE`
+|_auto-detected_
+|The namespace where the operator pod is running.
+
+|`POD_NAME`
+|_auto-detected_
+|The name of the operator pod.
+
+|`KAMEL_OPERATOR_ID`
+|`camel-k`
+|The operator ID used to identify which operator instance manages specific resources. Can also be set via `OPERATOR_ID`.
+
+|`KAMEL_BASE_IMAGE`
+|`eclipse-temurin:17-jdk`
+|The base image used for building Integration images. Can also be set via `RELATED_IMAGE_BASE`.
+
+|`CAMEL_K_SYNTHETIC_INTEGRATIONS`
+|`false`
+|When set to `true`, enables synthetic Integration support for managing external workloads.
+
+|`LOG_LEVEL`
+|`info`
+|The log level for the operator. Valid values: `debug`, `info`, `warn`, `error`.
+
+|`KAMELET_CATALOG_DIR`
+|`/tmp/kamelets/`
+|Directory where Kamelet catalog files are extracted during installation.
+|===