fix(release): point GHCR image.source at GitHub mirror

GHCR's package page auto-links to a GitHub repo via the
org.opencontainers.image.source label. The previous value
pointed at the Gitea canonical (somegit.dev/Owlibou/gnoma),
which GHCR can't resolve — so the package page just showed a
"Link this package to a repository" prompt and contributors,
Readme, and discussions never auto-populated.

Swap the two URL labels: source now points at the GitHub
mirror, url keeps the Gitea canonical reference. Both arch
build blocks updated.

Takes effect on the next release (v0.2.0 images already shipped
with the old labels and stay as-is).

.goreleaser.yml

@@ -55,8 +55,11 @@ dockers:
     build_flag_templates:
       - "--platform=linux/amd64"
       - "--label=org.opencontainers.image.title=gnoma"
-      - "--label=org.opencontainers.image.source=https://somegit.dev/Owlibou/gnoma"
-      - "--label=org.opencontainers.image.url=https://github.com/VikingOwl91/gnoma"
+      # image.source points at the GitHub mirror so GHCR auto-links the
+      # package page to the repo (Readme, contributors, discussions).
+      # The Gitea canonical URL stays available via image.url.
+      - "--label=org.opencontainers.image.source=https://github.com/VikingOwl91/gnoma"
+      - "--label=org.opencontainers.image.url=https://somegit.dev/Owlibou/gnoma"
       - "--label=org.opencontainers.image.version={{ .Version }}"
       - "--label=org.opencontainers.image.created={{ .Date }}"
       - "--label=org.opencontainers.image.revision={{ .FullCommit }}"
@@ -71,8 +74,11 @@ dockers:
     build_flag_templates:
       - "--platform=linux/arm64"
       - "--label=org.opencontainers.image.title=gnoma"
-      - "--label=org.opencontainers.image.source=https://somegit.dev/Owlibou/gnoma"
-      - "--label=org.opencontainers.image.url=https://github.com/VikingOwl91/gnoma"
+      # image.source points at the GitHub mirror so GHCR auto-links the
+      # package page to the repo (Readme, contributors, discussions).
+      # The Gitea canonical URL stays available via image.url.
+      - "--label=org.opencontainers.image.source=https://github.com/VikingOwl91/gnoma"
+      - "--label=org.opencontainers.image.url=https://somegit.dev/Owlibou/gnoma"
       - "--label=org.opencontainers.image.version={{ .Version }}"
       - "--label=org.opencontainers.image.created={{ .Date }}"
       - "--label=org.opencontainers.image.revision={{ .FullCommit }}"