feat(ui): add structured JSON logging to all server-side routes and lib

Introduces a logger.ts module emitting slog-compatible JSON lines to stderr.
Replaces silent catch blocks and console.error calls throughout minio.ts,
pocketbase.ts, hooks.server.ts, login, books, browse, and all API routes so
auth/registration failures, MinIO presign errors, and scraper proxy failures
are now visible in container logs.

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

@@ -1,11 +1,21 @@
 import type { PageServerLoad } from './$types';
 import { listBooks, allProgress } from '$lib/server/pocketbase';
+import { log } from '$lib/server/logger';
 
 export const load: PageServerLoad = async ({ locals }) => {
-	const [books, progressList] = await Promise.all([
-		listBooks(),
-		allProgress(locals.sessionId)
-	]);
+	let books: Awaited<ReturnType<typeof listBooks>>;
+	let progressList: Awaited<ReturnType<typeof allProgress>>;
+
+	try {
+		[books, progressList] = await Promise.all([
+			listBooks(),
+			allProgress(locals.sessionId)
+		]);
+	} catch (e) {
+		log.error('books', 'failed to load books or progress', { err: String(e) });
+		books = [];
+		progressList = [];
+	}
 
 	// Build a quick lookup: slug → last chapter read
 	const progressMap: Record<string, number> = {};