redfish: MSI support, fix zero dates, BMC MAC, Assembly FRU, crawler cleanup

- Add MSI CG480-S5063 (H100 SXM5) support:
  - collectGPUsFromProcessors: find GPUs via Processors/ProcessorType=GPU,
    resolve serials from Chassis/<GpuId>
  - looksLikeGPU: skip Description="Display Device" PCIe sidecars
  - isVirtualStorageDrive: filter AMI virtual USB drives (0-byte)
  - enrichNICMACsFromNetworkDeviceFunctions: pull MACs for MSI NICs
  - parseCPUs: filter by ProcessorType, parse Socket, L1/L2/L3 from ProcessorMemory
  - parseMemory: Location.PartLocation.ServiceLabel slot fallback
  - shouldCrawlPath: block /SubProcessors subtrees
- Fix status_checked_at/status_changed_at serializing as 0001-01-01:
  change all StatusCheckedAt/StatusChangedAt fields to *time.Time
- Redfish crawler cleanup:
  - Block non-inventory branches: AccountService, CertificateService,
    EventService, Registries, SessionService, TaskService, manager config paths,
    OperatingConfigs, BootOptions, HostPostCode, Bios/Settings, OEM KVM paths
  - Add Assembly to critical endpoints (FRU data)
  - Remove BootOptions from priority seeds
- collectBMCMAC: read BMC MAC from Managers/*/EthernetInterfaces
- collectAssemblyFRU: extract FRU serial/part from Chassis/*/Assembly
- Firmware: remove NetworkProtocol noise, fix SecureBoot field,
  filter BMCImageN redundant backup slots

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/server/device_repository.go

@@ -568,10 +568,10 @@ func mergeDevices(primary, secondary models.HardwareDevice) models.HardwareDevic
 	fillFloat(&primary.InputVoltage, secondary.InputVoltage)
 	fillInt(&primary.TemperatureC, secondary.TemperatureC)
 	fillString(&primary.Status, secondary.Status)
-	if primary.StatusCheckedAt.IsZero() && !secondary.StatusCheckedAt.IsZero() {
+	if primary.StatusCheckedAt == nil && secondary.StatusCheckedAt != nil {
 		primary.StatusCheckedAt = secondary.StatusCheckedAt
 	}
-	if primary.StatusChangedAt.IsZero() && !secondary.StatusChangedAt.IsZero() {
+	if primary.StatusChangedAt == nil && secondary.StatusChangedAt != nil {
 		primary.StatusChangedAt = secondary.StatusChangedAt
 	}
 	if primary.StatusAtCollect == nil && secondary.StatusAtCollect != nil {