feat: user profiles, subscriptions, and subscription feed

- PocketBase: new user_subscriptions collection (follower_id, followee_id)
- pocketbase.ts: subscribe/unsubscribe/getFollowingIds/getPublicProfile/
  getUserPublicLibrary/getUserCurrentlyReading/getSubscriptionFeed helpers
- GET /api/users/[username] — public profile with subscription state
- POST/DELETE /api/users/[username]/subscribe — follow/unfollow
- /users/[username] — public profile page: avatar, stats, follow button,
  currently reading grid, full library grid
- CommentsSection: usernames are now links to /users/[username]
- Home page: 'From People You Follow' section powered by subscription feed

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

@@ -3,7 +3,8 @@ import {
 	listBooks,
 	recentlyAddedBooks,
 	allProgress,
-	getHomeStats
+	getHomeStats,
+	getSubscriptionFeed
 } from '$lib/server/pocketbase';
 import { log } from '$lib/server/logger';
 import type { Book, Progress } from '$lib/server/pocketbase';
@@ -38,9 +39,18 @@ export const load: PageServerLoad = async ({ locals }) => {
 	const inProgressSlugs = new Set(continueReading.map((c) => c.book.slug));
 	const recentlyUpdated = recentBooks.filter((b) => !inProgressSlugs.has(b.slug)).slice(0, 6);
 
+	// Subscription feed — only when logged in
+	const subscriptionFeed = locals.user
+		? await getSubscriptionFeed(locals.user.id, 12).catch((e) => {
+				log.error('home', 'failed to load subscription feed', { err: String(e) });
+				return [] as Awaited<ReturnType<typeof getSubscriptionFeed>>;
+			})
+		: [];
+
 	return {
 		continueReading,
 		recentlyUpdated,
+		subscriptionFeed,
 		stats: {
 			...stats,
 			booksInProgress: continueReading.length