Fix: Resolve parsing error and svelte/no-at-html-tags linting issues

Resolved a critical parsing error in leads_view_lead.svelte due to incorrect Svelte class directive syntax.

Addressed multiple svelte/no-at-html-tags linting errors across the following files to mitigate potential XSS vulnerabilities and improve code safety:
- src/routes/events_leads/exhibit/[slug]/leads_add_scan.svelte
- src/routes/events_leads/exhibit/[slug]/leads_manage.svelte
- src/routes/events_leads/exhibit/[slug]/leads_view_lead.svelte

Replaced {@html} blocks with safer Svelte conditional rendering ({#if}) and direct interpolation ({value}) for static and dynamic content where appropriate. Removed commented-out {@html} tags that were still triggering linting errors.

src/routes/events_leads/exhibit/[slug]/leads_add_scan.svelte

@@ -293,9 +293,11 @@
 					$events_loc.leads.default_to_scan = !$events_loc.leads.default_to_scan;
 				}}
 			>
-				{@html $events_loc.leads.default_to_scan
-					? '<span class="fas fa-toggle-on m-1"></span> Disable Default Scan?'
-					: '<span class="fas fa-toggle-off m-1"></span> Enable Default Scan?'}
+				{#if $events_loc.leads.default_to_scan}
+					<span class="fas fa-toggle-on m-1"></span> Disable Default Scan?
+				{:else}
+					<span class="fas fa-toggle-off m-1"></span> Enable Default Scan?
+				{/if}
 			</button>
 
 			<button
@@ -309,9 +311,11 @@
 					$events_loc.leads.auto_view = !$events_loc.leads.auto_view;
 				}}
 			>
-				{@html $events_loc.leads.auto_view
-					? '<span class="fas fa-toggle-on m-1"></span> Disable Auto View?'
-					: '<span class="fas fa-toggle-off m-1"></span> Enable Auto View?'}
+				{#if $events_loc.leads.auto_view}
+					<span class="fas fa-toggle-on m-1"></span> Disable Auto View?
+				{:else}
+					<span class="fas fa-toggle-off m-1"></span> Enable Auto View?
+				{/if}
 			</button>
 
 			{#if $events_loc.leads.show_content__scan_requirements}
@@ -827,7 +831,7 @@
 				{/if}
 
 				<div class="qr_quick_results preset-tonal-secondary font-bold p-4">
-					{@html $events_sess.leads.qr_scan_result ?? 'No results yet'}
+					{$events_sess.leads.qr_scan_result ?? 'No results yet'}
 				</div>
 
 				<!-- This block needs to be moved or something. It takes up too much space! -->