Per-run module cache network analytics (bandwidth and fetch time) on the run detail page

The run detail page now shows network analytics for the module (binary) cache, so you can see how much data was moved and how fast, alongside the existing hit-rate numbers. On the Module Cache tab of a run you get a Summary card with total Downloaded and Uploaded bytes, plus Module Cache cards showing download and upload throughput (time-weighted average transfer speed). The Transfer, Latency, Throughput, and Fetch time widgets are interactive: each one can be selected to drive the time-series analytics chart, and the Transfer / Latency / Throughput widgets have a combined / downloads / uploads toggle (read / write for latency) to flip the headline value. This makes a slow or partial remote module cache fetch show up as a per-run outlier, instead of being hidden inside the hit-rate story.