feat: migrate CI/CD from GHCR to local Harbor registry

- Makefile: GHCR -> registry.celestium.life/stonks-oracle
- GitHub Actions: login to Harbor, use HARBOR_PASSWORD secret
- infra/k8s/*.yaml: all image refs -> registry.celestium.life
- inttest pipeline: remove GHCR pull secret (local registry, no auth)
- Steering docs: update registry/git endpoints

.github/workflows/build.yml

@@ -7,8 +7,8 @@ on:
     branches: [main]
 
 env:
-  REGISTRY: ghcr.io
-  IMAGE_BASE: ghcr.io/${{ github.repository_owner }}/stonks-oracle
+  REGISTRY: registry.celestium.life
+  IMAGE_BASE: registry.celestium.life/stonks-oracle
 
 jobs:
   lint-and-test:
@@ -83,12 +83,12 @@ jobs:
     steps:
       - uses: actions/checkout@v5
 
-      - name: Log in to GHCR
+      - name: Log in to Harbor
         uses: docker/login-action@v4
         with:
           registry: ${{ env.REGISTRY }}
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
+          username: admin
+          password: ${{ secrets.HARBOR_PASSWORD }}
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v4
@@ -117,12 +117,12 @@ jobs:
     steps:
       - uses: actions/checkout@v5
 
-      - name: Log in to GHCR
+      - name: Log in to Harbor
         uses: docker/login-action@v4
         with:
           registry: ${{ env.REGISTRY }}
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
+          username: admin
+          password: ${{ secrets.HARBOR_PASSWORD }}
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v4
@@ -149,12 +149,12 @@ jobs:
     steps:
       - uses: actions/checkout@v5
 
-      - name: Log in to GHCR
+      - name: Log in to Harbor
         uses: docker/login-action@v4
         with:
           registry: ${{ env.REGISTRY }}
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
+          username: admin
+          password: ${{ secrets.HARBOR_PASSWORD }}
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v4
@@ -217,8 +217,6 @@ jobs:
           kubectl cluster-info || echo "WARNING: kubectl cannot reach cluster API"
 
       - name: Run integration tests
-        env:
-          GHCR_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
           bash infra/inttest/run_pipeline.sh \
             --image-tag ${{ github.sha }} \