feat(scrape-range): add chapter range scraping for admin users

Adds FromChapter/ToChapter fields to orchestrator.Config and skips out-of-range
chapters in processBook. Exposes POST /scrape/book/range Go endpoint and a
matching UI proxy at /api/scrape/range. The book detail page now shows admins
a range input (from/to chapter) and a per-chapter 'scrape from here up' button.

ui/src/routes/api/scrape/range/+server.ts

@@ -0,0 +1,62 @@
+/**
+ * POST /api/scrape/range
+ *
+ * Proxies range-scrape requests to the Go scraper backend at POST /scrape/book/range.
+ * Admin-only.
+ *
+ * Request body (JSON):
+ *   { "url": "https://novelfire.net/book/...", "from": 50, "to": 100 }
+ *   "to" is optional — omit to scrape from "from" to the end.
+ *
+ * Responses mirror the Go scraper:
+ *   202  Accepted   — job enqueued
+ *   409  Conflict   — a scrape job is already running
+ *   400  Bad Request
+ *   403  Forbidden  — not an admin
+ */
+
+import { json, error } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { env } from '$env/dynamic/private';
+import { log } from '$lib/server/logger';
+
+const SCRAPER_URL = env.SCRAPER_API_URL ?? 'http://localhost:8080';
+
+export const POST: RequestHandler = async ({ request, locals }) => {
+	// Admin guard
+	if (!locals.user || locals.user.role !== 'admin') {
+		throw error(403, 'Forbidden');
+	}
+
+	let body: { url?: string; from?: number; to?: number } = {};
+	try {
+		body = await request.json();
+	} catch {
+		throw error(400, 'Invalid JSON body');
+	}
+
+	if (!body.url || typeof body.from !== 'number') {
+		throw error(400, 'url and from are required');
+	}
+
+	const upstream = `${SCRAPER_URL}/scrape/book/range`;
+	let res: Response;
+	try {
+		res = await fetch(upstream, {
+			method: 'POST',
+			headers: { 'Content-Type': 'application/json' },
+			body: JSON.stringify({ url: body.url, from: body.from, to: body.to })
+		});
+	} catch (e) {
+		log.error('scrape/range', 'scraper proxy network error', { err: String(e) });
+		throw error(502, 'Could not reach scraper');
+	}
+
+	if (!res.ok && res.status >= 500) {
+		const text = await res.text().catch(() => '');
+		log.error('scrape/range', 'scraper returned error', { status: res.status, body: text });
+	}
+
+	const data = await res.json().catch(() => ({}));
+	return json(data, { status: res.status });
+};