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/assistant.ts

@@ -116,10 +116,11 @@ export const assistantRouter = createTRPCRouter({
       const temperature = settings?.aiTemperature ?? 0.7;
       const model = settings?.azureOpenAiDeployment ?? "gpt-4o-mini";
 
-      // 2. Resolve granular permissions
+      // 2. Resolve granular permissions (using DB-based role defaults if available)
       const permissions = resolvePermissions(
         userRole as SystemRole,
         (ctx.dbUser?.permissionOverrides as PermissionOverrides | null) ?? null,
+        ctx.roleDefaults ?? undefined,
       );
       const permissionList = [...permissions];