Draw something for an icon or colour name nothing maps to

An unknown name indexed the map, got undefined and drew nothing — the same
as no icon at all, so a typo was invisible. It resolves to a placeholder
glyph and the default tint now, and warns once per bad name: both lookups
sit in a render, so a bound widget would otherwise warn per value.

An empty name still draws nothing, which is what "no icon" means.

frontend/src/components/Dashboard/ForecastWidget.tsx

@@ -1,6 +1,6 @@
 import { cn } from "@/lib/utils"
 import { useBoundValue } from "./dataContext"
-import { ICON_COLORS, ICONS } from "./icons"
+import { resolveIcon, resolveIconColor } from "./icons"
 import { config } from "./ui/core/config"
 import type { WidgetProps } from "./widgets"
 
@@ -41,7 +41,7 @@ export function ForecastWidget({ widget }: WidgetProps) {
   return (
     <div className="flex min-h-0 items-stretch justify-between gap-2">
       {items.map((item, index) => {
-        const Glyph = ICONS[item.icon ?? ""] ?? null
+        const Glyph = resolveIcon(item.icon ?? "")
         return (
           <div
             // Two steps can carry the same label and reading; position is the
@@ -66,7 +66,7 @@ export function ForecastWidget({ widget }: WidgetProps) {
               <Glyph
                 className={cn(
                   "dui-glyph-sm shrink-0",
-                  ICON_COLORS[item.color ?? ""] ?? ICON_COLORS.default,
+                  resolveIconColor(item.color ?? ""),
                 )}
               />
             ) : null}