Anchor derived trace exclusions for Litestar

Part of #156. On main, Litestar searches the exclusions unanchored (/api/metrics-report and /api/health/details produce no span) and misses the health check, because Litestar strips the trailing slash from scope["path"] (/health/ is traced as GET /health). #154 fixes the trailing slash but still searches unanchored. Blocked on #154, which rewrites the same Litestar exclusion code.