Skip Docker/publish workflows on forks

Add repository guard (github.repository == Nezreka/SoulSync) to
cleanup-dev-images, dev-nightly, and docker-publish workflows.
build-and-test stays available for fork contributors.

.github/workflows/cleanup-dev-images.yml

@@ -8,6 +8,7 @@ on:
 
 jobs:
   cleanup:
+    if: github.repository == 'Nezreka/SoulSync'
     runs-on: ubuntu-latest
     permissions:
       packages: write

.github/workflows/dev-nightly.yml

@@ -13,6 +13,7 @@ on:
 
 jobs:
   nightly:
+    if: github.repository == 'Nezreka/SoulSync'
     runs-on: ubuntu-latest
     # Skip scheduled runs if dev branch has no new commits in the last 24h
     # (pushes and manual triggers always run)

.github/workflows/docker-publish.yml

@@ -15,6 +15,7 @@ on:
 
 jobs:
   build-and-push:
+    if: github.repository == 'Nezreka/SoulSync'
     runs-on: ubuntu-latest
 
     permissions: