style: Phase 1+2 — FA→Lucide, variant-* → preset-*, dark mode forms

Phase 1 (global quick wins):
- app.css: add global dark mode utility for .input/.select/.textarea
- events menu nav + layout: replace all FontAwesome icons with Lucide
- events settings: replace FA icons, standardize variant-* → preset-*

Phase 2 (module-by-module migration):
- root +layout.svelte: fix hardcoded banner colors → preset-filled-error/warning
- journals entry list: replace slate-* with gray-*, HSL eye colors → CSS tokens
- pres mgmt presenter view: variant-soft-warning → preset-tonal-warning, FA edit → Lucide
- badges (4 files): variant-* → preset-*, FA spinner → Lucide Loader2, dynamic alert fix
- events session list + event hub: variant-soft/filled → preset-tonal/filled
- leads module (12 files): complete variant-* → preset-* migration across all
  exhibitor sign-in, QR scanner, manual search, tracking list, manage tab,
  custom questions, license list, exhibit page, lead detail page + form

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

src/routes/events/[event_id]/+page.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
     import { liveQuery } from 'dexie';
+    import { Wrench } from '@lucide/svelte';
     import { db_events } from '$lib/ae_events/db_events';
     import { ae_util } from '$lib/ae_utils/ae_utils';
     import { events_slct } from '$lib/stores/ae_events_stores';
@@ -93,9 +94,9 @@
     </div>
 
     {#if $ae_loc.administrator_access && $ae_loc.edit_mode}
-        <section class="card p-6 variant-soft-warning border-l-4 border-warning-500 mt-12 bg-surface-100 dark:bg-surface-800 shadow-lg">
+        <section class="card p-6 preset-tonal-warning border-l-4 border-warning-500 mt-12 shadow-lg">
             <div class="flex items-center gap-4">
-                <span class="fas fa-tools text-3xl"></span>
+                <Wrench size="2rem" class="shrink-0" aria-hidden="true" />
                 <div>
                     <h3 class="text-xl font-bold">Event Admin Settings</h3>
                     <p>You have elevated privileges. Use the menu above to access advanced settings and reports.</p>