feat(frontend): add EmailInput component with validation

EmailInput wraps shadcn Input with built-in validation (regex + browser checkValidity), normalization (trim + lowercase on blur), and inline error display. Follows PhoneInput.svelte pattern with  value/error and onvaluechange/onerrorchange/onblur callbacks.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

frontend/src/lib/components/ui/email-input/EmailInput.svelte

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+<script lang="ts">
+	import { Input } from '$lib/components/ui/input/index.js';
+	import { isValidEmail, normalizeEmail } from '$lib/utils/email';
+
+	interface Props {
+		value?: string;
+		error?: string;
+		placeholder?: string;
+		required?: boolean;
+		disabled?: boolean;
+		class?: string;
+		id?: string;
+		onvaluechange?: (value: string) => void;
+		onerrorchange?: (error: string) => void;
+		onblur?: () => void;
+	}
+
+	let {
+		value = $bindable(''),
+		error = $bindable(''),
+		placeholder = 'email@example.com',
+		required = false,
+		disabled = false,
+		class: className = '',
+		id = 'email',
+		onvaluechange,
+		onerrorchange,
+		onblur
+	}: Props = $props();
+
+	let touched = $state(false);
+
+	function handleInput(e: Event) {
+		const target = e.target as HTMLInputElement;
+		value = target.value;
+		onvaluechange?.(value);
+		if (touched) {
+			validate(value);
+		}
+	}
+
+	function handleBlur() {
+		touched = true;
+		const normalized = normalizeEmail(value);
+		if (normalized !== value) {
+			value = normalized;
+			onvaluechange?.(normalized);
+		}
+		validate(value);
+		onblur?.();
+	}
+
+	function validate(val: string) {
+		if (!val) {
+			if (required) {
+				error = 'Email is required';
+				onerrorchange?.(error);
+			} else {
+				error = '';
+				onerrorchange?.('');
+			}
+			return;
+		}
+		if (!isValidEmail(val)) {
+			error = 'Invalid email address';
+			onerrorchange?.(error);
+		} else {
+			error = '';
+			onerrorchange?.('');
+		}
+	}
+</script>
+
+<div class="space-y-1.5">
+	<Input
+		{id}
+		type="email"
+		inputmode="email"
+		autocomplete="email"
+		{placeholder}
+		{value}
+		oninput={handleInput}
+		onblur={handleBlur}
+		{disabled}
+		aria-invalid={!!error || undefined}
+		class={className}
+	/>
+	{#if error}
+		<p class="text-sm text-red-500">{error}</p>
+	{/if}
+</div>

frontend/src/lib/components/ui/email-input/index.ts

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+import EmailInput from './EmailInput.svelte';
+
+export { EmailInput };