fix: increase memory limit to 1Gi and set NODE_OPTIONS heap size

n8n 2.23+ has higher memory requirements. The previous 512Mi limit
caused OOM crashes (JS heap exhausted at ~248MB).

Changes:
- memory limit: 512Mi -> 1Gi, request: 256Mi -> 512Mi
- NODE_OPTIONS: --max-old-space-size={{ nodeHeapSizeMb }} (default 768MB)
  keeps JS heap at 75% of limit, leaving headroom for native code/buffers
- WEBHOOK_URL -> N8N_WEBHOOK_URL (deprecation warning fix)
- values.yaml: expose nodeHeapSizeMb for tuning

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

values.yaml

@@ -64,13 +64,18 @@ ingress:
   #      - n8n.local
 
 # Resource limits suitable for Raspberry Pi
+# n8n 2.23+ requires more memory. Set nodeHeapSizeMb to ~75% of memory limit.
 resources:
   limits:
     cpu: 1000m
-    memory: 512Mi
+    memory: 1Gi
   requests:
     cpu: 250m
-    memory: 256Mi
+    memory: 512Mi
+
+# Node.js heap size limit (MB). Should be ~75% of resources.limits.memory.
+# 1Gi limit → 768MB heap leaves headroom for native code and buffers.
+nodeHeapSizeMb: 768
 
 autoscaling:
   enabled: false