Phase 10: deployment (Apache compose + proxy fragments, CI release) + docs

- deploy/docker-compose.yml: pinned-tag ghcr image, hardened (cap_drop ALL +
  minimal cap_add, no-new-privileges, panel bound to 127.0.0.1 only). Apache
  itself runs on the host (spec 10.5), fragment at deploy/apache/.
- Alternative reverse-proxy fragments: nginx (+certbot sidecar), Caddy
  (automatic ACME), Traefik (+acme.json PEM extraction script).
- .github/workflows/release.yml: tag-triggered ghcr.io publish, version piped
  from the git tag into both the binary ldflags and the image tag (spec 10.1).
- Closed a gap from Phase 1: logrotate was installed but never invoked;
  wired up build/logrotate-mail.conf + logrotate-loop.sh + a supervisor
  program (copytruncate, since postlogd holds mail.log open with nothing to
  signal on rotation).
- README rewritten: site requirements checklist, reverse-proxy comparison,
  DNS setup (server- vs domain-level), IP warmup, backup/restore vs domain
  export/import, fixed-tag rationale, machine requirements.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.github/workflows/release.yml

@@ -0,0 +1,47 @@
+name: release
+
+# Publishes an immutable, version-tagged image on ghcr.io (spec 10.1).
+# Ordinary commits do not publish anything — only a pushed tag matching
+# vX.Y.Z does. That tag is the single source the version comes from: it goes
+# into both the image tag and the panel binary's -ldflags version, so the two
+# can never drift apart (the invariant restore's version check in spec 7.5.A
+# depends on).
+on:
+  push:
+    tags:
+      - "v[0-9]+.[0-9]+.[0-9]+"
+
+permissions:
+  contents: read
+  packages: write
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Derive version from tag
+        id: version
+        run: echo "version=${GITHUB_REF_NAME#v}" >> "$GITHUB_OUTPUT"
+
+      - uses: docker/setup-qemu-action@v3
+      - uses: docker/setup-buildx-action@v3
+
+      - name: Log in to ghcr.io
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: build/Dockerfile
+          platforms: linux/amd64,linux/arm64
+          build-args: |
+            VERSION=${{ steps.version.outputs.version }}
+          push: true
+          tags: ghcr.io/${{ github.repository }}:${{ steps.version.outputs.version }}