Explorer redesign Q: quick fixes, exact money, cache hardening, request dedupe

Spec §1.4 (items 1, 2, 9, 10, 11, 12) and §4.3.

• Wealth share column.
• Remove the fine categories grouping.
• lib/money.ts, replacing every parseFloat money sum.
• Viewer fail-soft path falls back to the player baseline.
• Government tab shown only to viewers with scope.
• .empty styling.
• Bounded L1 cache, a cold-miss cross-pod lock and maxStaleMs.
• React cache() dedupe for account and firm lookups and access checks, and a batched readableAccountIds.
• lib/pagination/cursor.ts.