fix(ci): align deploy-dev/deploy-uat frontend bump with base image name (CAR-1318)

The base frontend deployment in cartsnitch/infra uses
ghcr.io/cartsnitch/app, but the deploy-dev/deploy-uat jobs
targeted ghcr.io/cartsnitch/cartsnitch — a name that matches no
resource, so each bump added a dead images entry and left the
real 'app' entry's newTag pinned.

Switch both jobs to kustomize edit set image
ghcr.io/cartsnitch/app=... so the next deploy updates the active
entry. The matching infra overlay cleanup drops the dead
cartsnitch entry from dev/uat.

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

.gitea/workflows/ci.yml

@@ -495,7 +495,7 @@ jobs:
         if: needs.build-and-push.result == 'success'
         run: |
           cd infra/apps/overlays/dev
-          kustomize edit set image ghcr.io/cartsnitch/cartsnitch=git.farh.net/cartsnitch/cartsnitch:${{ steps.frontend_tag.outputs.tag }}
+          kustomize edit set image ghcr.io/cartsnitch/app=git.farh.net/cartsnitch/cartsnitch:${{ steps.frontend_tag.outputs.tag }}
 
       - name: Determine image tag for receiptwitness
         id: receiptwitness_tag
@@ -641,7 +641,7 @@ jobs:
         if: needs.build-and-push.result == 'success'
         run: |
           cd infra/apps/overlays/uat
-          kustomize edit set image ghcr.io/cartsnitch/cartsnitch=git.farh.net/cartsnitch/cartsnitch:${{ steps.frontend_tag.outputs.tag }}
+          kustomize edit set image ghcr.io/cartsnitch/app=git.farh.net/cartsnitch/cartsnitch:${{ steps.frontend_tag.outputs.tag }}
 
       - name: Determine image tag for receiptwitness
         id: receiptwitness_tag