fix: switch deploy containers from bitnami/kubectl to alpine/k8s

bitnami/kubectl lacks a package manager in the Gitea Actions runner,
so tool installation fails. alpine/k8s:1.32.3 ships with kubectl,
kustomize, git, jq, curl, and sed pre-installed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -170,11 +170,8 @@ jobs:
     runs-on: ubuntu-latest
     if: github.ref == 'refs/heads/main'
     container:
-      image: bitnami/kubectl:latest
+      image: alpine/k8s:1.32.3
     steps:
-      - name: Install required tools
-        run: |
-          apt-get update && apt-get install -y --no-install-recommends git ca-certificates
       - name: Checkout
         run: |
           git clone --depth=1 --branch=${GITHUB_REF_NAME} https://cameleer:${REGISTRY_TOKEN}@gitea.siegeln.net/${GITHUB_REPOSITORY}.git .
@@ -274,11 +271,8 @@ jobs:
     runs-on: ubuntu-latest
     if: github.ref != 'refs/heads/main' && github.event_name == 'push'
     container:
-      image: bitnami/kubectl:latest
+      image: alpine/k8s:1.32.3
     steps:
-      - name: Install required tools
-        run: |
-          apt-get update && apt-get install -y --no-install-recommends git jq sed ca-certificates
       - name: Checkout
         run: |
           git clone --depth=1 --branch=${GITHUB_REF_NAME} https://cameleer:${REGISTRY_TOKEN}@gitea.siegeln.net/${GITHUB_REPOSITORY}.git .
@@ -353,11 +347,8 @@ jobs:
     runs-on: ubuntu-latest
     if: github.event_name == 'delete' && github.event.ref_type == 'branch'
     container:
-      image: bitnami/kubectl:latest
+      image: alpine/k8s:1.32.3
     steps:
-      - name: Install required tools
-        run: |
-          apt-get update && apt-get install -y --no-install-recommends curl jq ca-certificates
       - name: Configure kubectl
         run: |
           mkdir -p ~/.kube