chore(ci): improve repository maintenance configuration

- Enable weekly Dependabot updates for GitHub Actions dependencies
- Consolidate duplicate Trivy scans into a single SARIF scan with exit-code gate
- Ignore macOS metadata and locally downloaded drone-ssh binaries
- Add feature request issue template and pull request checklist template

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/trivy-scan.yml

@@ -33,19 +33,10 @@ jobs:
           format: 'sarif'
           output: 'trivy-results.sarif'
           severity: 'CRITICAL,HIGH,MEDIUM'
+          exit-code: '1'
 
       - name: Upload Trivy results to GitHub Security tab
         uses: github/codeql-action/upload-sarif@v4
         if: always()
         with:
           sarif_file: 'trivy-results.sarif'
-
-      - name: Run Trivy vulnerability scanner (table format)
-        uses: aquasecurity/trivy-action@v0.36.0
-        with:
-          scan-type: 'fs'
-          scan-ref: '.'
-          scanners: 'vuln,secret,misconfig'
-          format: 'table'
-          severity: 'CRITICAL,HIGH,MEDIUM'
-          exit-code: '1'