Move general tasks + time reqs to Settings; add date adjustments

- Rename 'Category Settings' to 'Settings' (nav, page title, component)
- Move Recurring General Tasks and Time Requirements editing to Settings page
- Planner still loads both for calcRequired calculations
- Add date-specific Adjustments section to Planner: per-date +/- hour
  offsets keyed by YYYY-MM-DD (non-recurring); feed into Required Hours total
- Adjustments row shown in Required Hours tfoot when non-zero

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/Layout.tsx

@@ -31,7 +31,7 @@ export function Layout({ user, children }: Props) {
 
         <div style={{ flex: 1, padding: '0.5rem 0', overflowY: 'auto' }}>
           <NavItem to="/planner" icon={CalendarClock} label="Planner" />
-          {can(user, 'settings') && <NavItem to="/settings" icon={Settings} label="Category Settings" />}
+          {can(user, 'settings') && <NavItem to="/settings" icon={Settings} label="Settings" />}
         </div>
 
         <div style={{ padding: '0.75rem 1rem', borderTop: '1px solid var(--surface-2)' }}>