chore(ci): add version-bump.yml, decoupled from deploy

New workflow bumps pyproject.toml's version on PR merge, calling the
shared reusable-version-bump.yml (SIENTIAPDE-2217 version-bump reform) —
zero build/image/chart/deploy side effects. deploy.yml (workflow_dispatch-
only) will read this committed value instead of calculating one.

[skip ci]

.github/workflows/version-bump.yml

@@ -0,0 +1,14 @@
+name: Version Bump
+
+on:
+  pull_request:
+    types: [closed]
+    branches: [main, 'release/**', 'feature/**']
+
+jobs:
+  bump:
+    if: github.event.pull_request.merged == true
+    uses: Aignosi/github_workflow_templates/.github/workflows/reusable-version-bump.yml@main
+    with:
+      update_version_in: '["pyproject"]'
+    secrets: inherit