Update paperless-ngx to version 0.25.8

Bumped the paperless-ngx chart version from 0.25.7 to 0.25.8 in
Chart.yaml and updated the version badge in README.md to reflect
this change. The appVersion remains at 2.20.0.

Additionally, modified the type fields for readiness and liveness
probes in values.yaml from lowercase 'http' to uppercase 'HTTP'
for consistency and adherence to expected conventions. This change
ensures proper interpretation by Kubernetes. No breaking changes
have been introduced in this update.

charts/paperless-ngx/values.yaml

@@ -28,7 +28,7 @@ controllers:
           # 1. Readiness Probe (Wichtigste für den Traffic-Fluss)
           readiness:
             enabled: true
-            type: http # Verwendung des HTTP GET-Typs
+            type: HTTP # Verwendung des HTTP GET-Typs
             path: / # Prüft den Hauptpfad (Webserver antwortet nur, wenn DB/Redis verbunden sind)
             port: 8000 # Paperless-ngx läuft standardmäßig auf 8000
 
@@ -42,7 +42,7 @@ controllers:
           # 2. Liveness Probe (Wichtig für das Neustarten des Containers bei Absturz)
           liveness:
             enabled: true
-            type: http
+            type: HTTP
             path: /
             port: 8000