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/views/GraphView.vue

@@ -1,4 +1,5 @@
 <script setup lang="ts">
+import { X } from "lucide-vue-next";
 import { ref, onMounted, onUnmounted, watch, computed } from "vue";
 import { useRouter } from "vue-router";
 import { forceSimulation, forceLink, forceManyBody, forceX, forceY, forceCollide, SimulationNodeDatum, SimulationLinkDatum, Simulation } from "d3-force";
@@ -543,7 +544,7 @@ onUnmounted(() => {
                 :to="peekNode.type === 'task' ? `/tasks/${peekNode.id}/edit` : `/notes/${peekNode.id}/edit`"
                 class="peek-link"
               >Edit</router-link>
-              <button class="peek-close" @click="closePeek" title="Close (Esc)">✕</button>
+              <button class="peek-close" @click="closePeek" title="Close (Esc)"><X :size="16" /></button>
             </div>
           </div>