renovate: bump throttle 8/8 -> 16/16

26 items sat in dashboard "Rate-Limited" after the first default-allow
run (Sat 02:00); at 8 PRs/run + 1 run/week the backlog would take ~3
weeks to drain. Doubling to 16/16 cuts that to ~2 runs while still
leaving headroom (the dashboard "Pending Approval" majors and ghcr.io
"Pending Status Checks" don't count against this limit anyway).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

admin-system/renovate.yaml

@@ -44,8 +44,8 @@ data:
       "requireConfig": "optional",
       "dependencyDashboard": true,
       "dependencyDashboardTitle": "Renovate Dependency Dashboard",
-      "prHourlyLimit": 8,
-      "prConcurrentLimit": 8,
+      "prHourlyLimit": 16,
+      "prConcurrentLimit": 16,
       "enabledManagers": ["kubernetes", "helm-values"],
       "kubernetes": {
         "managerFilePatterns": ["/.+\\.ya?ml$/"]