webui: add persistent GPU settings management (ECC/MIG/CC/power limit)

Adds a GPU Settings card to /tools for the settings that actually
persist on NVIDIA data-center GPUs: ECC mode, MIG mode, and
Confidential Computing mode (all stored in the GPU's inforom/firmware,
take effect after a GPU reset or reboot) plus power limit (does not
persist — reapplied on demand). Includes a one-click "Reset All to
Defaults" that restores factory settings across every visible GPU,
touching only whatever has actually drifted.

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

audit/internal/app/app_test.go

@@ -235,6 +235,30 @@ func (f fakeSAT) ResetNvidiaGPU(index int) (string, error) {
 	return "", nil
 }
 
+func (f fakeSAT) ListNvidiaGPUSettings() ([]platform.NvidiaGPUSetting, error) {
+	return nil, nil
+}
+
+func (f fakeSAT) SetNvidiaGPUECC(index int, enabled bool) (string, error) {
+	return "", nil
+}
+
+func (f fakeSAT) SetNvidiaGPUMIG(index int, enabled bool) (string, error) {
+	return "", nil
+}
+
+func (f fakeSAT) SetNvidiaGPUCCMode(index int, enabled bool) (string, error) {
+	return "", nil
+}
+
+func (f fakeSAT) SetNvidiaGPUPowerLimit(index int, watts float64) (string, error) {
+	return "", nil
+}
+
+func (f fakeSAT) ResetNvidiaGPUDefaults() (string, error) {
+	return "", nil
+}
+
 func (f fakeSAT) RunMemoryAcceptancePack(_ context.Context, baseDir string, _, _ int, _ func(string)) (string, error) {
 	return f.runMemoryFn(baseDir)
 }