fix(workflows): add contents:read permission for checkout

Jobs with checkout steps need contents:read permission to access the repository.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: MarkusNeusinger

.github/workflows/bot-sync-status.yml

@@ -14,6 +14,7 @@ jobs:
   sync-status:
     runs-on: ubuntu-latest
     permissions:
+      contents: read
       issues: write
       pull-requests: read
 

.github/workflows/gen-new-plot.yml

@@ -111,6 +111,7 @@ jobs:
       pygal_issue: ${{ steps.create.outputs.pygal_issue }}
       highcharts_issue: ${{ steps.create.outputs.highcharts_issue }}
     permissions:
+      contents: read
       issues: write
 
     steps:
@@ -318,6 +319,7 @@ jobs:
     if: always() && needs.check-conditions.outputs.should_run == 'true'
     runs-on: ubuntu-latest
     permissions:
+      contents: read
       issues: write
 
     steps: