ci: CD auto-deploy via workflow_run trigger

- deploy.yaml now triggers automatically after successful CI completion
- Adds workflow_run event listener for 'CI - Build & Test'
- Guards deploy to only run when CI conclusion == success
- Preserves manual workflow_dispatch for targeted deploys
- Adds CI/CD note to README

.gitea/workflows/deploy.yaml

@@ -2,6 +2,10 @@ name: Deploy to Production
 run-name: 🚀 Deploy ${{ inputs.bump_version || 'patch' }} by @${{ gitea.actor }}
 
 on:
+  workflow_run:
+    workflows: ["CI - Build & Test"]
+    types: [completed]
+    branches: [main]
   workflow_dispatch:
     inputs:
       bump_version:
@@ -28,6 +32,7 @@ jobs:
   deploy:
     name: Deploy Nexus
     runs-on: deploy  # only on runners with 'deploy' label
+    if: ${{ gitea.event_name != 'workflow_run' || gitea.event.workflow_run.conclusion == 'success' }}
     steps:
       - name: Checkout latest code
         uses: actions/checkout@v3