rename: homelab-gateway → telegram-gateway

Aligns the project name with the public URL (tg.arcodange.fr) and the
Arcodange organization conventions. The 'homelab-gateway' name was too
generic.

Touches: chart name + helpers, image registry path, Go module path,
secret/configmap names, deployment mountPath, all docs.

chart/templates/configmap.yaml

@@ -1,10 +1,10 @@
 apiVersion: v1
 kind: ConfigMap
 metadata:
-  name: {{ include "homelab-gateway.fullname" . }}-bots
+  name: {{ include "telegram-gateway.fullname" . }}-bots
   namespace: {{ .Release.Namespace }}
   labels:
-    {{- include "homelab-gateway.labels" . | nindent 4 }}
+    {{- include "telegram-gateway.labels" . | nindent 4 }}
 data:
   bots.yaml: |
     bots: