fix: use named volume for prometheus config, populate on remote host

CHANGELOG.md

@@ -17,6 +17,10 @@
 - **Tag format**: Standardized on `*.*.*` (e.g. `1.0.9`), removed `v` prefix from existing tags.
 - **DEPLOYMENT.md**: Documented parallel CI/CD pipeline flow with workflow table.
 
+### Fixed
+
+- **Prometheus config mount**: Switched prod from bind mounts to named volume `prometheus-config`, populated via `docker run` on remote host. Fixes `not a directory` error when bind source path doesn't exist on deployment host.
+
 ### Removed
 
 - `.github/MEMORY.md`, `.github/agents/`, `.github/instructions/` — tracking files migrated out of repo.