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/__tests__/planAuditDescription.test.ts

@@ -0,0 +1,95 @@
+import { describe, it, expect } from "vitest";
+import {
+  planCategoryLabel,
+  buildPlanAuditDescription,
+} from "../utils/planAuditDescription";
+
+describe("planCategoryLabel", () => {
+  it("maps known plan categories to Czech labels", () => {
+    expect(planCategoryLabel("work")).toBe("Práce");
+    expect(planCategoryLabel("preparation")).toBe("Příprava");
+    expect(planCategoryLabel("travel")).toBe("Cesta / Montáž");
+    expect(planCategoryLabel("leave")).toBe("Dovolená");
+    expect(planCategoryLabel("sick")).toBe("Nemoc");
+    expect(planCategoryLabel("training")).toBe("Školení");
+    expect(planCategoryLabel("other")).toBe("Jiné");
+  });
+
+  it("falls back to the raw value for an unknown category", () => {
+    expect(planCategoryLabel("unknown_xyz")).toBe("unknown_xyz");
+  });
+});
+
+describe("buildPlanAuditDescription", () => {
+  it("describes a multi-day entry with project", () => {
+    const desc = buildPlanAuditDescription({
+      userName: "Jan Novák",
+      category: "work",
+      projectName: "Rekonstrukce haly",
+      dateFrom: "2026-06-08",
+      dateTo: "2026-06-12",
+    });
+    expect(desc).toBe(
+      "Jan Novák · 08.06.2026 – 12.06.2026 · Práce · Rekonstrukce haly",
+    );
+  });
+
+  it("collapses a single-day range to one date", () => {
+    const desc = buildPlanAuditDescription({
+      userName: "Jan Novák",
+      category: "work",
+      projectName: "Rekonstrukce haly",
+      dateFrom: "2026-06-08",
+      dateTo: "2026-06-08",
+    });
+    expect(desc).toBe("Jan Novák · 08.06.2026 · Práce · Rekonstrukce haly");
+  });
+
+  it("omits the project segment when there is no project", () => {
+    const desc = buildPlanAuditDescription({
+      userName: "Petr Svoboda",
+      category: "leave",
+      projectName: null,
+      dateFrom: "2026-06-10",
+      dateTo: "2026-06-10",
+    });
+    expect(desc).toBe("Petr Svoboda · 10.06.2026 · Dovolená");
+  });
+
+  it("appends the emergency-edit note when force is set", () => {
+    const desc = buildPlanAuditDescription({
+      userName: "Jan Novák",
+      category: "work",
+      projectName: null,
+      dateFrom: "2026-01-02",
+      dateTo: "2026-01-02",
+      force: true,
+    });
+    expect(desc).toBe("Jan Novák · 02.01.2026 · Práce · nouzová úprava");
+  });
+
+  it("appends a custom suffix (e.g. replaced override)", () => {
+    const desc = buildPlanAuditDescription({
+      userName: "Jan Novák",
+      category: "sick",
+      projectName: null,
+      dateFrom: "2026-06-10",
+      dateTo: "2026-06-10",
+      suffix: "nahrazeno novým záznamem",
+    });
+    expect(desc).toBe(
+      "Jan Novák · 10.06.2026 · Nemoc · nahrazeno novým záznamem",
+    );
+  });
+
+  it("treats a whitespace-only project name as no project", () => {
+    const desc = buildPlanAuditDescription({
+      userName: "Jan Novák",
+      category: "work",
+      projectName: "   ",
+      dateFrom: "2026-06-08",
+      dateTo: "2026-06-08",
+    });
+    expect(desc).toBe("Jan Novák · 08.06.2026 · Práce");
+  });
+});