feat(plan): render category colors from DB via --cat-color

Replace 14 hardcoded per-category CSS rules with a single --cat-color
custom property set inline on each filled cell button, driven by the DB
categories list threaded from PlanWork → PlanGrid → PlanRangeChips.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/components/PlanRangeChips.tsx

@@ -1,17 +1,19 @@
-import {
-  ResolvedCell,
-  planCategoryLabel,
-  cellProjectLabel,
-} from "../lib/queries/plan";
+import { ResolvedCell, cellProjectLabel } from "../lib/queries/plan";
 import type { Project } from "../lib/queries/projects";
 
 interface Props {
   cell: ResolvedCell | null;
   project: Project | null;
   readonly?: boolean;
+  categoryLabel: string;
 }
 
-export default function PlanRangeChips({ cell, project, readonly }: Props) {
+export default function PlanRangeChips({
+  cell,
+  project,
+  readonly,
+  categoryLabel,
+}: Props) {
   void readonly;
   if (!cell) return null;
   // Prefer the server-embedded project label (always present). Fall back to
@@ -27,9 +29,7 @@ export default function PlanRangeChips({ cell, project, readonly }: Props) {
   return (
     <div className="plan-chip-block">
       <div className="plan-chip-line">
-        <span className={`plan-chip plan-chip--${cell.category}`}>
-          {planCategoryLabel(cell.category)}
-        </span>
+        <span className="plan-chip">{categoryLabel}</span>
         {projectLabel && (
           <span className="plan-chip-project" title={projectTitle}>
             {projectLabel}