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>

packages/api/src/router/settings.ts

@@ -48,6 +48,8 @@ export const settingsRouter = createTRPCRouter({
       hasDalleApiKey: !!settings?.azureDalleApiKey,
       // Vacation defaults
       vacationDefaultDays: settings?.vacationDefaultDays ?? 28,
+      // Timeline
+      timelineUndoMaxSteps: settings?.timelineUndoMaxSteps ?? 50,
     };
   }),
 
@@ -94,6 +96,8 @@ export const settingsRouter = createTRPCRouter({
         azureDalleApiKey: z.string().optional(),
         // Vacation
         vacationDefaultDays: z.number().int().min(0).max(365).optional(),
+        // Timeline
+        timelineUndoMaxSteps: z.number().int().min(1).max(200).optional(),
       }),
     )
     .mutation(async ({ ctx, input }) => {
@@ -144,6 +148,8 @@ export const settingsRouter = createTRPCRouter({
         data.azureDalleApiKey = input.azureDalleApiKey || null;
       // Vacation
       if (input.vacationDefaultDays !== undefined) data.vacationDefaultDays = input.vacationDefaultDays;
+      // Timeline
+      if (input.timelineUndoMaxSteps !== undefined) data.timelineUndoMaxSteps = input.timelineUndoMaxSteps;
 
       await ctx.db.systemSettings.upsert({
         where: { id: "singleton" },