feat(panel): cascading columns, WB colour swatches, stronger HDF glow

Layout
- the panel is a cascade of columns: the rail's tabs, the tab's chips, the
  open chip's sub-chips, then the ruler. A child column no longer hides the
  column it came from (TEMP -> COLOR TEMP keeps TEMP visible); chips stack one
  per row instead of wrapping
- FRAME's WATERMARK opens its own column, so the frame chips stay put
- CREATE RECIPES gets the wide column its two-up form needs

WB colour swatches
- the ruler draws a colour box under the slider that follows the value:
  COLOR TEMP is the Kelvin colour (Tanner Helland), TINT runs green -10 ->
  neutral 0 -> magenta +10

HDF EFFECT
- knee 0.55..0.85 -> 0.45..0.75, blur 0.004+0.015n -> 0.006+0.024n of the
  width, screen alpha 0.15+0.35n -> 0.28+0.52n: a wide halo on the highlights
  instead of a hairline glow. Web copy of toneShader only — the phone keeps
  its own tuning.

Tabs
- rail order is PRESETS, FAVORITED, WB, LIGHT, FX, FRAME, CREATE RECIPES

docker/frontend/src/styles/tokens.css

@@ -6,7 +6,8 @@
   --radius: 10px;
   --radius-sm: 7px;
   --rail-w: 84px;
-  --chip-w: 300px;
+  --col-w: 168px;
+  --slider-w: 232px;
   --font: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
   --font-heading: var(--font);
   --mono: ui-monospace, SFMono-Regular, Menlo, monospace;