Color fires from ember to white-hot instead of blue to red

About 90% of detections are under 20 MW, so the old blue and teal
stops painted most of the map in cold colors that do not read as fire.
The ramp now runs ember, red, flame, orange, gold and white-hot at the
same thresholds, each stop lighter than the one below, so the brightest
marks are the strongest fires. The heatmap uses the same colors.

changelog.d/1426-fire-intensity-filter.md

@@ -1,9 +1,9 @@
 - Color every Active Fires detection by fire radiative power on a six-stop
-  cold → hot ramp (blue · teal · lime · amber · orange · red at 0 · 5 · 20 ·
-  50 · 100 · 300 MW), and add a log-scale minimum-FRP slider whose track is the
-  ramp, an All / Nominal+ / High confidence switch and an "N of M shown"
-  counter to the layer row. Far zoom shows a Snap Map–style heatmap instead
-  of squares, empty where nothing burns. The filter applies once before
-  rendering, so markers, cards, the heatmap, context and the top-fires query agree; share
+  ember → white-hot ramp (ember · red · flame · orange · gold · white-hot at
+  0 · 5 · 20 · 50 · 100 · 300 MW, brighter as power rises), and add a
+  log-scale minimum-FRP slider whose track is the ramp, an All / Nominal+ /
+  High confidence switch and an "N of M shown" counter to the layer row. Far
+  zoom shows a Snap Map–style heatmap in the same colors instead of squares,
+  empty where nothing burns. The filter applies once before rendering, so markers, cards, the heatmap, context and the top-fires query agree; share
   links keep it (`w` token: `f`, `c`), and `get_active_fires` takes matching
   `min_frp_mw` and `confidence` arguments. Default 0 MW / All (gekh, #1426).