ci: switch runner label from fabledcurator-ci to python-ci

Generic python-ci runner is reusable across the family (FabledScribe,
FabledSteward, NhenArchiver, StashHandler, etc.) rather than scoped to
just this project. Runner image lives at CI-Runner/CI-python/ in the
operator's workspace; pattern mirrors CI-Runner/CI-go and CI-Runner/CI-flutter.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -25,7 +25,7 @@ FabledCurator is designed to run inside a self-hosted homelab environment over p
 
 The repo's workflows expect:
 
-- **Runner label `fabledcurator-ci`** — a Forgejo runner with Python 3.14, ruff, and Node 22 pre-installed. Both `ci.yml` and `build.yml` use this label.
+- **Runner label `python-ci`** — a Forgejo runner with Python 3.14, ruff, and Node 22 pre-installed. Both `ci.yml` and `build.yml` use this label. The runner image (`runner-base:python-ci`) is built from `CI-Runner/CI-python/` in the operator's workspace; `make push` from that directory builds and pushes a new image when toolchain pins change.
 - **Repo secret `RELEASE_TOKEN`** — a Forgejo PAT with the following scopes:
   - `write:package` + `read:package` — for `docker push` to `git.fabledsword.com`
   - `write:release` — for future release-cutting workflows