tune Nextcloud Apache/PHP to fix constant crash-looping (50 restarts/6d)

Root cause: Apache prefork with 150 MaxRequestWorkers (each ~220MB RSS)
on SQLite DB causes worker exhaustion + lock contention → Apache hangs →
aggressive liveness probe (3 failures × 10s) kills container.

Fixes:
- Apache: MaxRequestWorkers 150→25, MaxConnectionsPerChild 0→200,
  StartServers 5→3 (via ConfigMap mount over mpm_prefork.conf)
- PHP: max_execution_time 0→300s, max_input_time 300s (prevent zombie workers)
- Liveness probe: period 10s→30s, failureThreshold 3→6, timeout 5s→10s
  (180s tolerance vs 30s before)
- Readiness probe: period 10s→30s, timeout 5s→10s

stacks/nextcloud/chart_values.yaml

@@ -18,10 +18,19 @@ nextcloud:
   extraEnv:
     - name: TRUSTED_PROXIES
       value: "10.0.0.0/8"
+    - name: PHP_MEMORY_LIMIT
+      value: "512M"
+    - name: PHP_UPLOAD_LIMIT
+      value: "16G"
     # - name: mail_smtpdebug
     #   value: "true"
     # - name: loglevel
     #   value: "0"
+  phpConfigs:
+    zzz-custom.ini: |
+      max_execution_time = 300
+      max_input_time = 300
+      default_socket_timeout = 300
 
 # internalDatabase:
 #   enabled: false
@@ -54,6 +63,22 @@ startupProbe:
   failureThreshold: 60
   successThreshold: 1
 
+livenessProbe:
+  enabled: true
+  initialDelaySeconds: 10
+  periodSeconds: 30
+  timeoutSeconds: 10
+  failureThreshold: 6
+  successThreshold: 1
+
+readinessProbe:
+  enabled: true
+  initialDelaySeconds: 10
+  periodSeconds: 30
+  timeoutSeconds: 10
+  failureThreshold: 3
+  successThreshold: 1
+
 podAnnotations:
   diun.enable: "true"
   diun.include_tags: "^[0-9]+(?:.[0-9]+)?(?:.[0-9]+)?.*"
@@ -71,3 +96,14 @@ resources:
 
 cronjob:
   enabled: true
+
+# Mount custom Apache MPM config to limit worker count
+extraVolumes:
+  - name: apache-tuning
+    configMap:
+      name: nextcloud-apache-tuning
+
+extraVolumeMounts:
+  - name: apache-tuning
+    mountPath: /etc/apache2/mods-enabled/mpm_prefork.conf
+    subPath: mpm_prefork.conf