fix(ci): workflow reliability and architecture improvements

- Reconstruct e2e-tests-split.yml to match spec (15 jobs, security isolation)
- Update docker-build.yml to authenticate Docker Hub for PRs (fixes 401)
- Refactor propagate-changes.yml to enforce strict hierarchy (Pittsburgh model)
- Implement API-based loop prevention to stop rebase loops

.github/workflows/benchmark.yml

@@ -5,12 +5,16 @@ on:
     branches:
       - main
       - development
+      - feature/**
+      - hotfix/**
     paths:
       - 'backend/**'
   pull_request:
     branches:
       - main
       - development
+      - feature/**
+      - hotfix/**
     paths:
       - 'backend/**'
   workflow_dispatch: