refactor(profile): extract PersonalInfoForm and PasswordChangeForm

Split profile/+page.svelte (240 lines) into:
- PersonalInfoForm.svelte: name/birth-date/email/contact with own date state
- PasswordChangeForm.svelte: current/new/confirm password fields

Page drops from 240 → ~25 lines.
Date utilities now imported from \$lib/utils/date instead of duplicated inline.

Part of #75

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/profile/PasswordChangeForm.svelte

@@ -0,0 +1,78 @@
+<script lang="ts">
+import { enhance } from '$app/forms';
+import { m } from '$lib/paraglide/messages.js';
+
+let {
+	form
+}: {
+	form?: { passwordSuccess?: boolean; passwordError?: string } | null;
+} = $props();
+</script>
+
+<div class="rounded-sm border border-line bg-surface p-6 shadow-sm">
+	<h2 class="mb-5 text-xs font-bold tracking-widest text-ink-3 uppercase">
+		{m.profile_section_password()}
+	</h2>
+
+	{#if form?.passwordSuccess}
+		<div class="mb-5 rounded border border-green-200 bg-green-50 p-3 text-sm text-green-700">
+			{m.profile_password_changed()}
+		</div>
+	{/if}
+	{#if form?.passwordError}
+		<div class="mb-5 rounded border border-red-200 bg-red-50 p-3 text-sm text-red-700">
+			{#if form.passwordError === 'PASSWORDS_DO_NOT_MATCH'}
+				{m.profile_password_mismatch()}
+			{:else}
+				{form.passwordError}
+			{/if}
+		</div>
+	{/if}
+
+	<form method="POST" action="?/changePassword" use:enhance>
+		<div class="space-y-4">
+			<label class="block">
+				<span class="mb-1 block font-sans text-xs font-bold tracking-widest text-ink-3 uppercase">
+					{m.profile_label_current_password()}
+				</span>
+				<input
+					type="password"
+					name="currentPassword"
+					required
+					class="w-full rounded-sm border border-line px-3 py-2 font-serif text-sm focus:border-ink focus:outline-none"
+				/>
+			</label>
+
+			<label class="block">
+				<span class="mb-1 block font-sans text-xs font-bold tracking-widest text-ink-3 uppercase">
+					{m.profile_label_new_password()}
+				</span>
+				<input
+					type="password"
+					name="newPassword"
+					required
+					class="w-full rounded-sm border border-line px-3 py-2 font-serif text-sm focus:border-ink focus:outline-none"
+				/>
+			</label>
+
+			<label class="block">
+				<span class="mb-1 block font-sans text-xs font-bold tracking-widest text-ink-3 uppercase">
+					{m.profile_label_new_password_confirm()}
+				</span>
+				<input
+					type="password"
+					name="confirmPassword"
+					required
+					class="w-full rounded-sm border border-line px-3 py-2 font-serif text-sm focus:border-ink focus:outline-none"
+				/>
+			</label>
+		</div>
+
+		<button
+			type="submit"
+			class="mt-5 rounded-sm bg-primary px-5 py-2 font-sans text-xs font-bold tracking-widest text-white uppercase transition-opacity hover:opacity-80"
+		>
+			{m.btn_save()}
+		</button>
+	</form>
+</div>