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]/(pres_mgmt)/presenter/[presenter_id]/presenter_view.svelte

@@ -1,4 +1,6 @@
 <script lang="ts">
+    import { Pencil } from '@lucide/svelte';
+
     interface Props {
         log_lvl?: number;
         // export let event_presenter_id: string;
@@ -866,11 +868,10 @@
 
         <button type="button"
             title="Edit your passcode"
-            class="btn btn-sm variant-soft-warning"
+            class="btn btn-sm preset-tonal-warning"
             class:hidden={!$ae_loc.trusted_access}
             >
-            <span class="fas fa-edit">
-            </span>
+            <Pencil size="1em" aria-hidden="true" />
             Edit
         </button> -->
             </li>