Build multi-arch (amd64+arm64) Docker images with PostgreSQL support (#793)

* Build multi-arch Docker images with PostgreSQL support

The prebuilt image now installs the `[postgresql]` extra, so the optional
PostgreSQL output backend (psycopg) works out of the box in the container
without a separate `pip install` (#792). The wheel path is resolved into a
variable before appending the extra so the shell doesn't treat
`*.whl[postgresql]` as a bracket glob.

The build workflow now sets up QEMU + Buildx and builds a multi-arch
manifest for `linux/amd64` and `linux/arm64`, so the image runs natively on
64-bit ARM hosts such as a Raspberry Pi (#789). Every compiled dependency
(psycopg[binary], lxml, maxminddb, cryptography) ships prebuilt aarch64
manylinux wheels, so the arm64 build adds no source-compilation step.

A `pull_request` trigger (scoped to the build inputs) and `workflow_dispatch`
are added so the multi-arch build can be validated on PRs and rebuilt on
demand; pushes are still gated on the release event, so neither pushes images.

Closes #789
Closes #792

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Bump version to 10.0.4 to publish the new images

The docker workflow only pushes to the registry on a `release` event, so
shipping the multi-arch + PostgreSQL-enabled image requires cutting a
release. 10.0.3 is already tagged, so bump to 10.0.4 and document the
Docker changes in the changelog.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Don't run the docker build on pull requests

The pull_request trigger (added to validate the multi-arch build) re-ran the
full ~10-minute amd64+arm64 build on every commit pushed to a docker-touching
PR, because the pull_request `paths` filter matches against the PR's entire
diff, not just the newest commit. That is wasteful once the build has been
validated.

Drop the pull_request trigger and rely on workflow_dispatch for on-demand
validation (plus the existing master-push and release triggers). Also gate the
registry login on the release event so that no non-release run authenticates
to ghcr at all — a build can only ever be pushed from a published release.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -27,7 +27,14 @@ COPY --from=build /app/dist/*.whl /tmp/dist/
 RUN set -ex; \
     groupadd --gid ${USER_GID} ${USERNAME}; \
     useradd --uid ${USER_UID} --gid ${USER_GID} -m ${USERNAME}; \
-    pip install /tmp/dist/*.whl; \
+    # Install the wheel with the [postgresql] extra so the prebuilt image
+    # ships the PostgreSQL output backend (psycopg). Resolve the globbed wheel
+    # path into a variable first: `*.whl[postgresql]` would otherwise be parsed
+    # as a shell bracket glob rather than a pip extras spec. psycopg[binary]
+    # has prebuilt manylinux wheels for both amd64 and arm64, so this adds no
+    # source-build step on either platform.
+    whl="$(ls /tmp/dist/*.whl)"; \
+    pip install "${whl}[postgresql]"; \
     rm -rf /tmp/dist
 
 USER $USERNAME