Add explicit permissions to all actions workflows (#36140)

Explicitely specify all workflow
[`permissions`](https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#permissions).
This will fix [26 CodeQL
alerts](https://github.com/go-gitea/gitea/security/code-scanning?query=permissions+is%3Aopen+branch%3Amain+).

.github/workflows/cron-licenses.yml

@@ -9,6 +9,8 @@ jobs:
   cron-licenses:
     runs-on: ubuntu-latest
     if: github.repository == 'go-gitea/gitea'
+    permissions:
+      contents: write
     steps:
       - uses: actions/checkout@v6
       - uses: actions/setup-go@v6