Basis rebuilt: faster data, cleaner numbers, per-client sources

The previous Basis (former Centro) connection loaded data live from the API every time a report opened, which meant slow widgets and frequent drops. The rebuilt integration stores data instead, so reports load reliably and breakdowns that weren't available before (tactic and line item group) are now supported.

Spend figures now align with Basis billing totals, including added value line items, so what clients see in Basis matches what you show them in Whatagraph.