fix(cartsnitch): deploy-dev/deploy-uat checkout ref must match PR base (CAR-1374)

Parameterize the actions/checkout ref for cartsnitch/infra in deploy-dev
and deploy-uat so the head branch lineage matches the PR base:
  - main push -> ref: main, base: main (unchanged)
  - dev push  -> ref: dev,  base: dev
  - uat push  -> ref: uat,  base: uat

Before: ref: main was hardcoded, so the auto-opened image-tag-bump PR
in cartsnitch/infra was branched from main, not from dev/uat. With the
CAR-1371 base=dev/base=uat change, the diff ballooned to 30+ files and
the PR was unmergeable (see cartsnitch/infra#392).

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.gitea/workflows/ci.yml

@@ -484,7 +484,7 @@ jobs:
         with:
           repository: cartsnitch/infra
           token: ${{ secrets.CI_GITEA_TOKEN }}
-          ref: main
+          ref: ${{ github.ref == 'refs/heads/main' && 'main' || (github.ref == 'refs/heads/uat' && 'uat' || 'dev') }}
           path: infra
 
       - name: Install kubectl
@@ -630,7 +630,7 @@ jobs:
         with:
           repository: cartsnitch/infra
           token: ${{ secrets.CI_GITEA_TOKEN }}
-          ref: main
+          ref: ${{ github.ref == 'refs/heads/main' && 'main' || (github.ref == 'refs/heads/uat' && 'uat' || 'dev') }}
           path: infra
 
       - name: Install kubectl