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/EventSlideOver.vue

@@ -1,4 +1,5 @@
 <script setup lang="ts">
+import { X } from "lucide-vue-next";
 import { ref, computed, watch, onMounted, onUnmounted } from "vue";
 import { createEvent, updateEvent, deleteEvent, type EventEntry, type EventCreatePayload, type EventUpdatePayload } from "@/api/client";
 import ProjectSelector from "@/components/ProjectSelector.vue";
@@ -259,7 +260,7 @@ async function doDelete() {
       <div class="slide-over-panel" role="dialog" aria-modal="true">
         <div class="so-header">
           <h2 class="so-title">{{ isEditMode ? "Edit Event" : "New Event" }}</h2>
-          <button class="so-close" @click="emit('close')" aria-label="Close">✕</button>
+          <button class="so-close" @click="emit('close')" aria-label="Close"><X :size="16" /></button>
         </div>
 
         <form class="so-form" @submit.prevent="save">
@@ -316,7 +317,7 @@ async function doDelete() {
             <div class="color-row">
               <input v-model="color" type="color" class="color-picker" title="Pick event color" />
               <input v-model="color" class="so-input color-hex" placeholder="#5B4A8A" />
-              <button v-if="color" type="button" class="btn-clear-color" @click="color = ''">✕</button>
+              <button v-if="color" type="button" class="btn-clear-color" @click="color = ''"><X :size="16" /></button>
             </div>
           </div>