sync file-type support across upload/convert and fix collected_at timezone handling

internal/models/models.go

@@ -13,6 +13,7 @@ type AnalysisResult struct {
 	SourceType  string          `json:"source_type,omitempty"`  // archive | api
 	Protocol    string          `json:"protocol,omitempty"`     // redfish | ipmi
 	TargetHost  string          `json:"target_host,omitempty"`  // BMC host for live collect
+	SourceTimezone string       `json:"source_timezone,omitempty"` // Source timezone/offset used during collection (e.g. +08:00)
 	CollectedAt time.Time       `json:"collected_at,omitempty"` // Collection/upload timestamp
 	RawPayloads map[string]any  `json:"raw_payloads,omitempty"` // Additional source payloads (e.g. Redfish tree)
 	Events      []Event         `json:"events"`