feat(design): surface phase PR 1 — Lucide icon migration + scale enforcement

Replaces every hand-inlined SVG in the chrome (60 across 15 files)
with Lucide components. Snaps icon sizes to the doc's 16/24 scale —
all icons in this pass land at 16. AppLogo wordmark stays as the
legitimate "custom app icon" exception per the doc; GraphView's <svg>
mount point for D3 stays as well.

Replaces emoji-as-icons in clear button-affordance cases with their
Lucide equivalents: ✕ → X (close/dismiss buttons across 8 files), ✓ →
Check (ProjectView task-advance button), 🎤 → Mic (ChatPanel voice
CTA), 📎 → Paperclip (ChatView context toggle), &uarr; → ArrowUp
(ChatInputBar Send), &times; → X (ChatPanel context-note remove), ☀/☾
→ Sun/Moon (AppHeader theme toggle).

Inline emoji punctuation in textual confirmation copy ("Saved ✓",
"Created ✓", `done: "✓"` status maps, `'✓' : '📄'` interpolations)
is left for surface-phase voice/tone touchups — replacing requires
structural template changes and is best done per-component.

Stroke weight stays at Lucide's default 2px; tightening to the doc's
1.5/1 is deferred per the surface-phase spec (option ii: drop-in +
scale enforcement).

Adds lucide-vue-next ^0.469.0 to frontend/package.json. Docker
rebuild handles the install.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/NotificationBell.vue

@@ -2,6 +2,7 @@
 import { ref, onMounted, onUnmounted } from 'vue'
 import { useNotificationsStore } from '@/stores/notifications'
 import NotificationsPanel from './NotificationsPanel.vue'
+import { Bell } from 'lucide-vue-next'
 
 const store = useNotificationsStore()
 const open = ref(false)
@@ -45,10 +46,7 @@ onUnmounted(() => {
       aria-label="Notifications"
       :title="`${store.count} unread notification${store.count !== 1 ? 's' : ''}`"
     >
-      <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
-        <path d="M18 8A6 6 0 0 0 6 8c0 7-3 9-3 9h18s-3-2-3-9"/>
-        <path d="M13.73 21a2 2 0 0 1-3.46 0"/>
-      </svg>
+      <Bell :size="16" aria-hidden="true" />
       <span v-if="store.count > 0" class="bell-badge" aria-live="polite">{{ store.count > 99 ? '99+' : store.count }}</span>
     </button>
     <NotificationsPanel v-if="open" @close="close" />