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/utils/dashboardHelpers.ts

@@ -34,6 +34,8 @@ export const ENTITY_TYPE_LABELS: Record<string, string> = {
   trips: "Jízda",
   vehicles: "Vozidlo",
   bank_account: "Bankovní účet",
+  work_plan_entry: "Plán prací – záznam",
+  work_plan_override: "Plán prací – přepsání dne",
 };
 
 export const ACTION_LABELS: Record<string, string> = {