chore(ci): revert consolidated pipeline and restore individual workflow triggers

Reverts the experimental consolidated CI pipeline strategy in favor of independent, parallel workflows triggered on pull requests.

- Removed .github/workflows/ci-pipeline.yml
- Restored 'on: pull_request' triggers to:
  - docker-build.yml
  - cerberus-integration.yml
  - crowdsec-integration.yml
  - rate-limit-integration.yml
  - waf-integration.yml
  - e2e-tests-split.yml
- Updated integration workflows to build local Docker images instead of expecting artifacts
- Fixed invalid 'env' context usage in e2e-tests-split.yml conditions

.github/workflows/docker-build.yml

@@ -21,6 +21,14 @@ name: Docker Build, Publish & Test
 # See: docs/plans/current_spec.md (Section 4.1 - docker-build.yml changes)
 
 on:
+  push:
+    branches:
+      - main
+      - development
+  pull_request:
+    branches:
+      - main
+      - development
   workflow_dispatch:
 
 concurrency: