Short design covering four changes: mtime-based CSS cache-bust token, Django Debug Toolbar (dev-only) for profiling, N+1 fixes on Dashboard and Payroll pages, and a before/after measurement in the commit message. Scope is deliberately tight — plan B (template splitting) and plan C (full audit) are deferred until plan A evidence lands. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>