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/PlanGrid.tsx

@@ -1,5 +1,12 @@
 import { useMemo } from "react";
-import { GridData, ResolvedCell, planCategoryLabel } from "../lib/queries/plan";
+import type { CSSProperties } from "react";
+import {
+  GridData,
+  ResolvedCell,
+  planCategoryLabel,
+  categoryMap,
+  PlanCategory,
+} from "../lib/queries/plan";
 import type { Project } from "../lib/queries/projects";
 import PlanRangeChips from "./PlanRangeChips";
 
@@ -7,6 +14,7 @@ interface Props {
   data: GridData | undefined;
   canEdit: boolean;
   projects: Project[];
+  categories: PlanCategory[];
   // The (userId, date) of the most recent successful mutation. The
   // matching cell gets a one-shot highlight pulse. `nonce` is part of
   // the value so back-to-back mutations on the same cell re-trigger
@@ -92,10 +100,12 @@ export default function PlanGrid({
   data,
   canEdit,
   projects,
+  categories,
   pulseKey,
   onCellClick,
 }: Props) {
   const today = useMemo(() => todayIso(), []);
+  const catMap = useMemo(() => categoryMap(categories), [categories]);
 
   if (!data)
     return (
@@ -206,10 +216,17 @@ export default function PlanGrid({
                       <button
                         type="button"
                         className={cls}
+                        style={
+                          cell
+                            ? ({
+                                "--cat-color": catMap[cell.category]?.color,
+                              } as CSSProperties)
+                            : undefined
+                        }
                         onClick={() => onCellClick(u.id, date, cell)}
                         aria-label={
                           cell
-                            ? `${u.full_name}, ${date}, ${planCategoryLabel(cell.category)}`
+                            ? `${u.full_name}, ${date}, ${planCategoryLabel(cell.category, catMap)}`
                             : isLocked
                               ? `${u.full_name}, ${date}, ${past ? "uplynulý den" : "prázdné"} — bez záznamu`
                               : `${u.full_name}, ${date}, prázdné — přidat záznam`
@@ -225,6 +242,9 @@ export default function PlanGrid({
                               : null
                           }
                           readonly={!canEdit}
+                          categoryLabel={
+                            cell ? planCategoryLabel(cell.category, catMap) : ""
+                          }
                         />
                       </button>
                     </td>