Constant MAX_BUDGET_DIMENSIONS 

pub const MAX_BUDGET_DIMENSIONS: usize = 64;

Single source of truth for the budget dimension cap (#104).

Enforced at both the HTTP boundary in ff-server (which re-exports this constant) and inside the typed FCALL wrappers below, so direct script-helper callers (tests, tools, alternate services) cannot reach Valkey with an unbounded dim_count by skipping the REST layer.

64 is generously above any legitimate scoping dimension count (org/tenant/project/region/lane/tier/…) while bounding worst-case FCALL ARGV to ~200 strings — well below Valkey argv limits.