fix: enable CI on feature branches and add workflow_dispatch (#13)

Fixes PRI-524. Changes push trigger from branches:[main] to branches:['**'] so CI fires on every branch. Adds workflow_dispatch for manual trigger. Adds permissions: contents: read for least-privilege hardening.

All gates clear: CI green, UAT correctly skipped (YAML-only), QA approved (Regina), CTO approved (Nancy).

.github/workflows/ci.yaml

@@ -2,9 +2,13 @@ name: CI
 
 on:
   push:
-    branches: [main]
+    branches: ['**']
   pull_request:
     branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
 
 jobs:
   ci: