feat: timeline multi-select, demand popover, resource hover card, merged tooltips, dark mode fixes

Major timeline enhancements:
- Right-click drag multi-selection with floating action bar (batch delete/assign)
- DemandPopover for demand strip details (replaces broken "Loading" modal)
- ResourceHoverCard on name hover showing skills, rates, role, chapter
- Merged heatmap+vacation tooltips into unified TimelineTooltip component
- Fixed overbooking blink animation (date normalization, z-index ordering)
- Fixed dark mode sticky column bleed-through in project view
- System roles admin page, notification task management, performance review docs

Co-Authored-By: claude-flow <ruv@ruv.net>

apps/web/src/components/timeline/TimelineContext.tsx

@@ -145,6 +145,7 @@ export interface TimelineContextValue {
   // ─ Display preferences
   displayMode: TimelineDisplayMode;
   heatmapScheme: HeatmapColorScheme;
+  blinkOverbookedDays: boolean;
 
   // ─ Loading
   isLoading: boolean;
@@ -287,6 +288,7 @@ export function TimelineProvider({
   const { prefs: appPrefs } = useAppPreferences();
   const displayMode = appPrefs.timelineDisplayMode;
   const heatmapScheme = appPrefs.heatmapColorScheme;
+  const blinkOverbookedDays = appPrefs.blinkOverbookedDays;
 
   // ─── Data queries ──────────────────────────────────────────────────────────
   const { data: entriesView, isLoading } = trpc.timeline.getEntriesView.useQuery(
@@ -300,7 +302,7 @@ export function TimelineProvider({
       ...(filters.countryCodes.length > 0 ? { countryCodes: filters.countryCodes } : {}),
     },
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    { placeholderData: (prev: any) => prev },
+    { placeholderData: (prev: any) => prev, refetchOnWindowFocus: false, staleTime: 90_000 },
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
   ) as { data: TimelineEntriesView | undefined; isLoading: boolean };
 
@@ -309,7 +311,7 @@ export function TimelineProvider({
 
   const { data: vacationEntries = [] } = trpc.vacation.list.useQuery(
     { startDate: viewStart, endDate: viewEnd, status: [VacationStatus.APPROVED, VacationStatus.PENDING], limit: 500 },
-    { placeholderData: (prev) => prev },
+    { placeholderData: (prev) => prev, refetchOnWindowFocus: false, staleTime: 90_000 },
   );
 
   const vacationsByResource = useMemo(() => {
@@ -593,6 +595,7 @@ export function TimelineProvider({
       today,
       displayMode,
       heatmapScheme,
+      blinkOverbookedDays,
       isLoading,
       isInitialLoading,
       totalAllocCount,
@@ -618,6 +621,7 @@ export function TimelineProvider({
       today,
       displayMode,
       heatmapScheme,
+      blinkOverbookedDays,
       isLoading,
       isInitialLoading,
       totalAllocCount,