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.

eslint.config.js

@@ -0,0 +1,38 @@
+// @ts-check
+
+import eslint from '@eslint/js';
+import tseslint from 'typescript-eslint';
+import svelte from 'eslint-plugin-svelte';
+import prettier from 'eslint-config-prettier';
+import globals from 'globals';
+
+export default tseslint.config(
+	eslint.configs.recommended,
+	...tseslint.configs.recommended,
+	svelte.configs['flat/recommended'],
+	prettier,
+	{
+		languageOptions: {
+			globals: {
+				...globals.browser,
+				...globals.node
+			}
+		}
+	},
+	{
+		files: ['**/*.svelte'],
+		languageOptions: {
+			parserOptions: {
+				parser: tseslint.parser
+			}
+		}
+	},
+	{
+		ignores: ['build/', '.svelte-kit/', 'node_modules/']
+	},
+	{
+		rules: {
+			'@typescript-eslint/no-unused-vars': 'warn'
+		}
+	}
+);