fix(ci): add workflow_dispatch trigger and fix push path filter

Also adds ci.yml to the push paths filter so a change to the workflow
itself triggers a validation run (catches the fix in the previous commit).

Co-Authored-By: Claude <noreply@anthropic.com>

Author: davidamacey

.github/workflows/ci.yml

@@ -17,6 +17,8 @@ on:
     branches: [main]
     paths:
       - "services/**/docker-compose.yml"
+      - ".github/workflows/ci.yml"
+  workflow_dispatch:    # Allow manual trigger from Actions tab
 
 jobs:
   validate: