feat: profile page, admin pages, infinite scroll on browse

- Add /profile page with reading settings (voice, speed, auto-next) and password change form
- Add /admin/scrape page showing scraping task history with live status polling and trigger controls
- Add /admin/audio page showing audio cache entries with client-side search filter
- Add changePassword(), listAudioCache(), listScrapingTasks() to pocketbase.ts
- Add /api/admin/scrape and /api/browse-page server-side proxy routes
- Replace browse page pagination with IntersectionObserver infinite scroll
- Update nav: username becomes a /profile link; admin users see Scrape and Audio cache links

ui/src/routes/profile/+page.server.ts

@@ -0,0 +1,50 @@
+import { fail, redirect } from '@sveltejs/kit';
+import type { Actions, PageServerLoad } from './$types';
+import { changePassword } from '$lib/server/pocketbase';
+import { log } from '$lib/server/logger';
+
+export const load: PageServerLoad = async ({ locals }) => {
+	if (!locals.user) {
+		redirect(302, '/login');
+	}
+	return {
+		user: locals.user
+	};
+};
+
+export const actions: Actions = {
+	changePassword: async ({ request, locals }) => {
+		if (!locals.user) {
+			return fail(401, { error: 'Not logged in.' });
+		}
+
+		const data = await request.formData();
+		const current = (data.get('current') as string | null) ?? '';
+		const next = (data.get('next') as string | null) ?? '';
+		const confirm = (data.get('confirm') as string | null) ?? '';
+
+		if (!current || !next || !confirm) {
+			return fail(400, { error: 'All fields are required.' });
+		}
+		if (next.length < 8) {
+			return fail(400, { error: 'New password must be at least 8 characters.' });
+		}
+		if (next !== confirm) {
+			return fail(400, { error: 'New passwords do not match.' });
+		}
+
+		let ok: boolean;
+		try {
+			ok = await changePassword(locals.user.id, current, next);
+		} catch (e) {
+			log.error('profile', 'changePassword failed', { err: String(e) });
+			return fail(500, { error: 'An error occurred. Please try again.' });
+		}
+
+		if (!ok) {
+			return fail(401, { error: 'Current password is incorrect.' });
+		}
+
+		return { success: true };
+	}
+};