feat(03-05): mount EventForm + add New Event FAB/toolbar trigger in CalendarShell

- Import EventForm and Plus icon from lucide-react
- Phone: fixed FAB bottom-right (56px, dark neutral fill per UI-SPEC)
- Tablet/desktop: toolbar button above calendar content area
- Both trigger setEventForm(true, 'create') via Zustand
- EventForm conditionally rendered while eventFormOpen
- Selectors pattern preserved to avoid unnecessary re-renders (Bug B guard)

apps/pwa/src/components/CalendarShell.tsx

@@ -39,12 +39,14 @@ import {
   type CalendarType,
 } from '@schedule-x/calendar'
 import { createEventsServicePlugin } from '@schedule-x/events-service'
+import { Plus } from 'lucide-react'
 
 import { fetchMe, fetchEvents } from '../api/client.js'
 import { hydrateEvents } from '../lib/hydrateEvents.js'
 import { buildCalendarConfig, SX_FIRST_DAY_OF_WEEK } from '../lib/calendarConfig.js'
 import { useCalendarStore } from '../store/calendarStore.js'
 import { EventDetailPopover } from './EventDetailPopover.js'
+import { EventForm } from './EventForm.js'
 import { AppNav } from './AppNav.js'
 import { ColorLegend } from './ColorLegend.js'
 import { SkeletonCalendar } from './SkeletonCalendar.js'
@@ -75,6 +77,8 @@ export function CalendarShell() {
   const setCalendarRange = useCalendarStore((s) => s.setCalendarRange)
   const setOpenEventId = useCalendarStore((s) => s.setOpenEventId)
   const selectedView = useCalendarStore((s) => s.selectedView)
+  const setEventForm = useCalendarStore((s) => s.setEventForm)
+  const eventFormOpen = useCalendarStore((s) => s.eventFormOpen)
   const { start, end } = calendarRange
   const queryClient = useQueryClient()
 
@@ -297,7 +301,7 @@ export function CalendarShell() {
   // ── Full layout ────────────────────────────────────────────────────────────
 
   if (phone) {
-    // Phone: stacked layout — AppNav top bar + content below
+    // Phone: stacked layout — AppNav top bar + content below + FAB
     return (
       <div
         style={{
@@ -318,6 +322,37 @@ export function CalendarShell() {
         <InstallPrompt />
         <CalendarContent />
         <EventDetailPopover />
+
+        {/* New Event FAB — phone: bottom-right floating action button (UI-SPEC §Interaction Contract) */}
+        <button
+          aria-label="New Event"
+          onClick={() => setEventForm(true, 'create')}
+          style={{
+            position: 'fixed',
+            bottom: 'var(--space-6)',
+            right: 'var(--space-6)',
+            width: '56px',
+            height: '56px',
+            minWidth: '56px',
+            minHeight: '56px',
+            borderRadius: '50%',
+            background: 'var(--color-text-primary)',
+            color: '#ffffff',
+            border: 'none',
+            cursor: 'pointer',
+            display: 'flex',
+            alignItems: 'center',
+            justifyContent: 'center',
+            boxShadow: '0 4px 16px rgba(0,0,0,0.18)',
+            zIndex: 100,
+            fontFamily: 'var(--font-family-base)',
+          }}
+        >
+          <Plus size={24} aria-hidden="true" />
+        </button>
+
+        {/* EventForm modal — conditionally rendered while eventFormOpen */}
+        {eventFormOpen && <EventForm />}
       </div>
     )
   }
@@ -345,11 +380,50 @@ export function CalendarShell() {
       {/* Main content area */}
       <div style={{ flex: 1, minWidth: 0, display: 'flex', flexDirection: 'column', overflow: 'hidden' }}>
         <InstallPrompt />
+
+        {/* New Event toolbar button — tablet/desktop (UI-SPEC §Interaction Contract) */}
+        <div
+          style={{
+            display: 'flex',
+            justifyContent: 'flex-end',
+            padding: 'var(--space-2) var(--space-4)',
+            borderBottom: '1px solid var(--color-border-subtle)',
+            background: 'var(--color-surface)',
+            flexShrink: 0,
+          }}
+        >
+          <button
+            onClick={() => setEventForm(true, 'create')}
+            style={{
+              background: 'var(--color-text-primary)',
+              color: '#ffffff',
+              border: 'none',
+              cursor: 'pointer',
+              minHeight: '44px',
+              padding: '0 var(--space-4)',
+              borderRadius: 'var(--space-1)',
+              fontSize: 'var(--text-label-size)',
+              fontWeight: 600,
+              display: 'flex',
+              alignItems: 'center',
+              gap: 'var(--space-1)',
+              fontFamily: 'var(--font-family-base)',
+            }}
+          >
+            <Plus size={16} aria-hidden="true" />
+            {/* Plain text — XSS guard */}
+            New Event
+          </button>
+        </div>
+
         <CalendarContent />
       </div>
 
       {/* EventDetailPopover — standalone mode driven by Zustand openEventId */}
       <EventDetailPopover />
+
+      {/* EventForm modal — conditionally rendered while eventFormOpen */}
+      {eventFormOpen && <EventForm />}
     </div>
   )
 }