fix(plan): readable audit descriptions, project labels, dashboard invalidation, view-only & sticky-column UI

Work-plan fixes from this session:
- Czech audit descriptions for plan entries/overrides (was empty '-')
- server-embedded project label on grid cells (was '-' past the 100-project cap)
- dashboard activity + audit-log cache invalidation on plan mutations
- read-only cells: no '+' on empty, keep hover on cells with a record
- view modal: Czech category + formatted dates
- sticky date column made opaque (no bleed-through on horizontal scroll)

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

src/admin/components/PlanRangeChips.tsx

@@ -1,4 +1,8 @@
-import { ResolvedCell } from "../lib/queries/plan";
+import {
+  ResolvedCell,
+  planCategoryLabel,
+  cellProjectLabel,
+} from "../lib/queries/plan";
 import type { Project } from "../lib/queries/projects";
 
 interface Props {
@@ -7,34 +11,24 @@ interface Props {
   readonly?: boolean;
 }
 
-const CATEGORY_LABELS: Record<string, string> = {
-  work: "Práce",
-  preparation: "Příprava",
-  travel: "Cesta / Montáž",
-  leave: "Dovolená",
-  sick: "Nemoc",
-  training: "Školení",
-  other: "Jiné",
-};
-
 export default function PlanRangeChips({ cell, project, readonly }: Props) {
   void readonly;
   if (!cell) return null;
-  const projectLabel = project
+  // Prefer the server-embedded project label (always present). Fall back to
+  // the looked-up `project` prop only if the cell predates the embed (stale
+  // cache).
+  const fallbackLabel = project
     ? project.project_number
       ? `${project.project_number} — ${project.name}`
       : project.name
     : null;
-  const projectTitle = project
-    ? project.project_number
-      ? `${project.project_number} — ${project.name}`
-      : project.name
-    : undefined;
+  const projectLabel = cellProjectLabel(cell) ?? fallbackLabel;
+  const projectTitle = projectLabel ?? undefined;
   return (
     <div className="plan-chip-block">
       <div className="plan-chip-line">
         <span className={`plan-chip plan-chip--${cell.category}`}>
-          {CATEGORY_LABELS[cell.category] ?? cell.category}
+          {planCategoryLabel(cell.category)}
         </span>
         {projectLabel && (
           <span className="plan-chip-project" title={projectTitle}>