Clarify current patrons and add granular dashboard totals

[bt1142msstate]

Summary

• define current patrons as unexpired or non-expiring accounts and reconcile expired/unknown records
• add complete system and branch totals with privacy suppression
• expose per-metric calculations, source fields, grain, and time basis
• distinguish all-record patron geography from current-patron metrics
• add exact item/title, inventory, location, availability, and turnover presentation

Validation

• production backend dashboard suite: 196 tests passed
• frontend architecture and unit suites: 302 tests passed
• browser smoke and authenticated production visual checks passed
• production collection reconciliation: 3,575,162 items and 1,798,064 exact titles
• production patron reconciliation: 621,976 records = 158,348 current + 453,982 expired + 9,646 unknown