Adds a colour-coded progress bar showing heapUsed as a percentage of the V8 heap size limit (green < 70%, amber 70-85%, red >= 85%) plus a status line (Healthy / Elevated / Critical), so the criticality of a site's memory is visible at a glance rather than read from the raw table. Uses the data the page already fetches from /api/health/memory; the heap-versus-limit ratio is what actually drives the GC-thrash slowness, so that is what the gauge tracks.