fix: Remove registry prefix from repo paths in Woodpecker

The docker-buildx plugin automatically prepends registry to repo,
so having the full URL caused doubled paths:
reg.mosaicstack.dev/reg.mosaicstack.dev/mosaic/api

Changed from: repo: reg.mosaicstack.dev/mosaic/api
Changed to:   repo: mosaic/api

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.woodpecker.yml

@@ -88,7 +88,7 @@ steps:
     image: woodpeckerci/plugin-docker-buildx
     settings:
       registry: reg.mosaicstack.dev
-      repo: reg.mosaicstack.dev/mosaic/api
+      repo: mosaic/api
       dockerfile: apps/api/Dockerfile
       context: .
       platforms:
@@ -110,7 +110,7 @@ steps:
     image: woodpeckerci/plugin-docker-buildx
     settings:
       registry: reg.mosaicstack.dev
-      repo: reg.mosaicstack.dev/mosaic/web
+      repo: mosaic/web
       dockerfile: apps/web/Dockerfile
       context: .
       platforms:
@@ -134,7 +134,7 @@ steps:
     image: woodpeckerci/plugin-docker-buildx
     settings:
       registry: reg.mosaicstack.dev
-      repo: reg.mosaicstack.dev/mosaic/postgres
+      repo: mosaic/postgres
       dockerfile: docker/postgres/Dockerfile
       context: docker/postgres
       platforms: