⚡ Bolt: Replace O(n) array filtering with O(log n) binary search in time-series lookups

[toreleon]

💡 What: Replaces the O(n) .filter() array scanning with an O(log n) findLastBarIndex() binary search utility for time-series lookups in backtestRunner.ts and dnsePublic.ts.
🎯 Why: During backtesting, the runtime needs to repeatedly fetch the price of a ticker "as of" the simulated time. Previously, this was done using .filter((b) => b.time <= asOf) which created a new array and checked every single element. Since time-series data is already sorted chronologically, this created an unnecessary bottleneck of $O(T \times N)$ operations where $T$ is the number of intervals and $N$ is the number of historical price bars.
📊 Impact: Reduces algorithmic complexity of historical time lookups from $O(n)$ to $O(\log n)$. For a dataset of 1,000 bars, this requires at most ~10 checks instead of exactly 1,000 element scans plus array allocations per simulation step per stock ticker.
🔬 Measurement: Verified using existing test suite (pnpm test) to ensure lookups yield exact same output. Type integrity verified via pnpm typecheck.

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PR created automatically by Jules for task 18229871251248953845 started by @toreleon

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