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/app/globals.css

@@ -335,7 +335,7 @@
   color: rgb(196 181 253) !important;
 }
 .dark .bg-amber-50 {
-  background-color: rgb(120 53 15 / 0.2) !important;
+  background-color: rgb(120 53 15) !important;
 }
 
 /* Modal / overlay */
@@ -427,3 +427,19 @@
     @apply opacity-75 shadow-lg scale-105;
   }
 }
+
+/* ─── Overbooking blink animation ──────────────────────────────────────────── */
+@keyframes overbooking-blink {
+  0%, 100% { background-color: rgba(239, 68, 68, 0); }
+  50% { background-color: rgba(239, 68, 68, 0.18); }
+}
+.dark .animate-overbooking-blink {
+  animation: overbooking-blink-dark 2s ease-in-out infinite;
+}
+@keyframes overbooking-blink-dark {
+  0%, 100% { background-color: rgba(239, 68, 68, 0); }
+  50% { background-color: rgba(239, 68, 68, 0.25); }
+}
+.animate-overbooking-blink {
+  animation: overbooking-blink 2s ease-in-out infinite;
+}