feat: add Docker Hub as primary registry for anonymous pulls

GHCR requires authentication even for public packages on some systems.
CI now pushes to both GHCR and Docker Hub. docker-compose.yml and Helm
chart point to Docker Hub where anonymous pulls always work. Build
directives kept as fallback for source-based builds.

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

helm/chart/values.yaml

@@ -13,7 +13,7 @@ shadowbroker:
             runAsGroup: 1001
           image:
             pullPolicy: Always
-            repository: ghcr.io/bigbodycobain/shadowbroker-backend
+            repository: bigbodycobain/shadowbroker-backend
             tag: latest
           env:
             AIS_API_KEY:
@@ -41,7 +41,7 @@ shadowbroker:
             runAsGroup: 1001
           image:
             pullPolicy: Always
-            repository: ghcr.io/bigbodycobain/shadowbroker-frontend
+            repository: bigbodycobain/shadowbroker-frontend
             tag: latest
 
           env: