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>

.forgejo/workflows/build.yml

@@ -12,7 +12,7 @@ on:
 
 jobs:
   build-web:
-    runs-on: fabledcurator-ci
+    runs-on: python-ci
     steps:
       - uses: actions/checkout@v4
 
@@ -41,7 +41,7 @@ jobs:
           tags: ${{ steps.tag.outputs.tags }}
 
   build-ml:
-    runs-on: fabledcurator-ci
+    runs-on: python-ci
     steps:
       - uses: actions/checkout@v4