Add private billing-related allocation attributes

[QuanMPhm]

As described in the daily usage showback document, we want to add several billing-related attributes to help keep track of each allocation's monetary costs and alert users:

• Daily Charges for Month: A private JSON-encoded string containing a list of key-value pairs that shows the daily costs for an allocation by SU type:

"daily": {
	"2025-10-02": {
		"OpenShift CPU": "3.60",
		"OpenShift GPUA100SXM4": "124.00"
		},
	"2025-10-03": {
		"OpenShift CPU": "10.65",
		"OpenShift GPUA100SXM4": "326.00"
		}
	}
}

• Project Alert & Allocation Alert : A dollar amount at which the PI would want to be alerted. If either attributes are present, the PI should be alerted once all-time costs reaches said amount
• Previous Charges - Will store in JSON format a key-value pair of the charges for previous months, as defined in the final invoices.

"previous": {
	"2025-09": {
		"OpenShift CPU": "10.65",
		"OpenShift GPUA100SXM4": "326.00"
	}
}