Update postgres Docker tag to v18

jarrs-system/jarr-dev.yaml

@@ -81,7 +81,7 @@ spec:
         fsGroup: 999
       containers:
         - name: postgres
-          image: postgres:16-alpine
+          image: postgres:18-alpine
           imagePullPolicy: IfNotPresent
           env:
             - name: POSTGRES_USER

workout-system/sparkyfitness.yaml

@@ -69,7 +69,7 @@ spec:
         fsGroup: 999
       containers:
         - name: postgres
-          image: postgres:15-alpine
+          image: postgres:18-alpine
           env:
             - name: POSTGRES_USER
               valueFrom:
@@ -168,7 +168,7 @@ spec:
               echo "PostgreSQL is ready!"
       containers:
         - name: server
-          image: codewithcj/sparkyfitness_server:v0.16.9
+          image: codewithcj/sparkyfitness_server:v0.16.8
           env:
             # ---- Database (owner / superuser role, used for migrations) ----
             - name: SPARKY_FITNESS_DB_HOST