chore(main): release google-cloud-alloy_db-v1alpha 0.18.0 (#32348)

* chore(main): release google-cloud-alloy_db-v1alpha 0.18.0

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: release-please[bot]

.release-please-manifest.json

@@ -55,7 +55,7 @@
   "google-cloud-alloy_db+FILLER": "0.0.0",
   "google-cloud-alloy_db-v1": "1.6.2",
   "google-cloud-alloy_db-v1+FILLER": "0.0.0",
-  "google-cloud-alloy_db-v1alpha": "0.17.1",
+  "google-cloud-alloy_db-v1alpha": "0.18.0",
   "google-cloud-alloy_db-v1alpha+FILLER": "0.0.0",
   "google-cloud-alloy_db-v1beta": "0.20.1",
   "google-cloud-alloy_db-v1beta+FILLER": "0.0.0",

google-cloud-alloy_db-v1alpha/CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+### 0.18.0 (2026-01-13)
+
+#### Features
+
+* add POSTGRES_18 to DatabaseVersion ([#32335](https://github.com/googleapis/google-cloud-ruby/issues/32335)) 
+
 ### 0.17.1 (2025-10-27)
 
 #### Documentation

google-cloud-alloy_db-v1alpha/lib/google/cloud/alloy_db/v1alpha/version.rb

@@ -21,7 +21,7 @@ module Google
   module Cloud
     module AlloyDB
       module V1alpha
-        VERSION = "0.17.1"
+        VERSION = "0.18.0"
       end
     end
   end

google-cloud-alloy_db-v1alpha/snippets/snippet_metadata_google.cloud.alloydb.v1alpha.json

@@ -1,7 +1,7 @@
 {
   "client_library": {
     "name": "google-cloud-alloy_db-v1alpha",
-    "version": "0.17.1",
+    "version": "0.18.0",
     "language": "RUBY",
     "apis": [
       {