fix: use FORGEJO_TOKEN instead of REGISTRY_PAT for git auth

Forgejo auto-injects GITHUB_TOKEN secret. Use FORGEJO_TOKEN env var
for clarity since we're retiring GitHub.

.gitea/workflows/ci.yaml

@@ -18,7 +18,7 @@ jobs:
     env:
       GOPRIVATE: forgejo.riotpiao.com
       GOFLAGS: -mod=readonly
-      REGISTRY_PAT: ${{ secrets.REGISTRY_PAT }}
+      FORGEJO_TOKEN: ${{ secrets.GITHUB_TOKEN }}
     steps:
       - name: install node (required by JS-based actions)
         run: apt-get update && apt-get install -y --no-install-recommends nodejs ca-certificates git
@@ -27,7 +27,7 @@ jobs:
 
       - name: configure git auth for private module fetch
         run: |
-          git config --global url."https://oauth2:${REGISTRY_PAT}@forgejo.riotpiao.com".insteadOf "https://forgejo.riotpiao.com"
+          git config --global url."https://oauth2:${FORGEJO_TOKEN}@forgejo.riotpiao.com".insteadOf "https://forgejo.riotpiao.com"
 
       - name: cache go modules + build cache
         uses: actions/cache@v4