fix: merge database blocks to avoid duplicate YAML key

Combine Neo4j memory tuning and port override into a single
database service block.

docker-compose.override.yml

@@ -16,17 +16,14 @@ services:
       - SYS_MODULE
     restart: unless-stopped
 
-  # === Neo4j memory tuning ===
-  database:
-    environment:
-      - NEO4J_dbms_memory_transaction_total_max=4G
-      - NEO4J_server_memory_heap_max__size=4G
-
   # === Infrahub ===  
   message-queue:
     ports: !override
       []
   database:
+    environment:
+      - NEO4J_dbms_memory_transaction_total_max=4G
+      - NEO4J_server_memory_heap_max__size=4G
     ports: !override
       []
   infrahub-server: