Bump pihole/pihole from 2026.02.0 to 2026.04.0 in /docker (#57)

Bumps pihole/pihole from 2026.02.0 to 2026.04.0.

---
updated-dependencies:
- dependency-name: pihole/pihole
  dependency-version: 2026.04.0
  dependency-type: direct:production
...

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Author: dependabot[bot]

docker/docker-compose.yml

@@ -14,7 +14,7 @@ services:
 
   pihole:
     container_name: pihole
-    image: pihole/pihole:2026.02.0
+    image: pihole/pihole:2026.04.0
     hostname: pihole
     networks:
       macvlan: