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]/(badges)/badges/ae_comp__badge_create_form.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
     // import { createEventDispatcher } from 'svelte';
+    import { Loader2 } from '@lucide/svelte';
     import type { key_val } from '$lib/stores/ae_stores';
     import { events_func } from '$lib/ae_events_functions';
     import { ae_api } from '$lib/stores/ae_stores';
@@ -126,16 +127,16 @@
     <div class="flex justify-end gap-2">
         <button
             type="button"
-            class="btn variant-filled-tertiary"
+            class="btn preset-tonal-surface"
             onclick={handle_cancel}>Cancel</button
         >
         <button
             type="submit"
-            class="btn variant-filled-primary"
+            class="btn preset-filled-primary"
             disabled={submit_status === 'loading'}
         >
             {#if submit_status === 'loading'}
-                <span class="fas fa-spinner fa-spin mr-2"></span>
+                <Loader2 size="1em" class="animate-spin" aria-hidden="true" />
             {/if}
             Create Badge
         </button>

src/routes/events/[event_id]/(badges)/badges/ae_comp__badge_upload_form.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
     // import { createEventDispatcher } from 'svelte';
+    import { Loader2 } from '@lucide/svelte';
     import type { key_val } from '$lib/stores/ae_stores';
     import { events_func } from '$lib/ae_events_functions';
     import { ae_api } from '$lib/stores/ae_stores';
@@ -159,9 +160,9 @@
 
     {#if upload_status !== 'idle'}
         <div
-            class="alert variant-soft-{upload_status === 'error'
-                ? 'error'
-                : 'info'}"
+            class="alert"
+            class:preset-tonal-error={upload_status === 'error'}
+            class:preset-tonal-surface={upload_status !== 'error'}
         >
             <p>{upload_message}</p>
             {#if upload_status === 'processing' || upload_status === 'loading'}
@@ -180,20 +181,20 @@
     <div class="flex justify-end gap-2">
         <button
             type="button"
-            class="btn variant-filled-tertiary"
+            class="btn preset-tonal-surface"
             onclick={handle_cancel}
             disabled={upload_status === 'loading' ||
                 upload_status === 'processing'}>Cancel</button
         >
         <button
             type="submit"
-            class="btn variant-filled-primary"
+            class="btn preset-filled-primary"
             disabled={!selected_file ||
                 upload_status === 'loading' ||
                 upload_status === 'processing'}
         >
             {#if upload_status === 'loading' || upload_status === 'processing'}
-                <span class="fas fa-spinner fa-spin mr-2"></span>
+                <Loader2 size="1em" class="animate-spin" aria-hidden="true" />
             {/if}
             Upload Badges
         </button>