Reorganize CI/CD bootstrap phases and add custom runner Dockerfile (#50)

## Summary
- Reorder CI/CD bootstrap phases to address chicken-and-egg problem
- P2 is now "Custom Runner Image" (stock runner lacks Node.js)
- Add P3 for "Mirror Forgejo & Build from Source"
- Rename P3 -> P4 (Self-Deploy), P4 -> P5 (Container Builds)
- Add Dockerfile for custom runner with Node.js, npm, docker, build tools
- Update overview with new phase structure, host mode notes, and cross-compilation challenge

## Key Changes

### Phase Reordering
| Old | New | Name |
|-----|-----|------|
| P1 | P1 | Enable Actions (complete) |
| P2 | P2 | **Custom Runner Image** (new focus) |
| - | P3 | **Mirror Forgejo & Build** (new) |
| P3 | P4 | Self-Deploy |
| P4 | P5 | Container Builds |

### Custom Runner Dockerfile
The stock `forgejo/runner:3.5.1` image lacks Node.js, so `actions/checkout@v4` doesn't work. The new Dockerfile adds:
- Node.js + npm (for GitHub Actions)
- Docker CLI (for container builds)
- Build tools (gcc, make, curl, jq)

### Bootstrap Strategy
1. Build custom runner image manually on gilbert (podman build)
2. Push to zot registry
3. Update deployment to use custom image
4. Then enable auto-build workflow for runner

## Deployment and Testing
- [x] Review plan changes
- [x] Build custom runner image manually and verify
- [x] Update runner deployment
- [x] Test `actions/checkout@v4` works

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://forge.tail8d86e.ts.net/eblume/blumeops/pulls/50

.forgejo/workflows/test.yaml

@@ -10,24 +10,35 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - name: Checkout (git clone)
-        run: |
-          # For PRs use head_ref (branch name), for pushes use ref_name
-          BRANCH="${HEAD_REF:-$REF_NAME}"
-          git clone --depth 1 --branch "$BRANCH" \
-            "${SERVER_URL}/${REPOSITORY}.git" .
-        env:
-          GIT_SSL_NO_VERIFY: "true"
-          HEAD_REF: ${{ github.head_ref }}
-          REF_NAME: ${{ github.ref_name }}
-          SERVER_URL: ${{ github.server_url }}
-          REPOSITORY: ${{ github.repository }}
+      - name: Checkout
+        uses: actions/checkout@v4
 
-      - name: Hello World
+      - name: Verify tools
+        run: |
+          echo "=== Node.js ==="
+          node --version
+          npm --version
+          echo ""
+          echo "=== Git ==="
+          git --version
+          echo ""
+          echo "=== Build tools ==="
+          make --version | head -1
+          gcc --version | head -1
+          echo ""
+          echo "=== Docker ==="
+          docker --version
+          echo ""
+          echo "=== Other tools ==="
+          curl --version | head -1
+          jq --version
+
+      - name: Show repo info
         run: |
-          echo "Hello from Forgejo Actions!"
-          echo "Runner: $(hostname)"
           echo "Repository: ${{ github.repository }}"
           echo "Event: ${{ github.event_name }}"
           echo "Ref: ${{ github.ref }}"
+          echo "Branch: ${{ github.ref_name }}"
+          echo ""
+          echo "=== Files ==="
           ls -la