Add Puppeteer browser scraping and HG Spot store config

- Add browser-scraper.ts using Puppeteer for JS-heavy stores
- Add render_js flag to store model, migration, YAML sync, and UI
- Scraper engine auto-selects cheerio vs Puppeteer based on flag
- Store forms include JS rendering toggle in Advanced section
- Create first store config: HG Spot (Croatian electronics retailer)
- Update Dockerfile with Chromium for production Puppeteer support

Tested: HG Spot returns 15 products per page with correct names,
prices (EUR), links, and images using headless browser rendering.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server/scraper/browser-scraper.ts

@@ -0,0 +1,115 @@
+import puppeteer, { type Browser } from 'puppeteer';
+import type { Store } from '../models/store.js';
+import type { ScrapedItem } from './result-parser.js';
+
+let browser: Browser | null = null;
+
+const PAGE_TIMEOUT = 30_000;
+const NAVIGATION_TIMEOUT = 20_000;
+
+async function getBrowser(): Promise<Browser> {
+  if (browser && browser.connected) return browser;
+
+  browser = await puppeteer.launch({
+    headless: true,
+    args: [
+      '--no-sandbox',
+      '--disable-setuid-sandbox',
+      '--disable-dev-shm-usage',
+      '--disable-gpu',
+      '--disable-extensions',
+      '--no-first-run',
+    ],
+  });
+
+  return browser;
+}
+
+export interface BrowserScrapeResult {
+  items: ScrapedItem[];
+  html: string;
+  statusCode: number;
+}
+
+export async function scrapeStoreWithBrowser(store: Store, searchUrl: string): Promise<BrowserScrapeResult> {
+  const b = await getBrowser();
+  const page = await b.newPage();
+
+  try {
+    // Set user agent if configured
+    if (store.user_agent) {
+      await page.setUserAgent(store.user_agent);
+    }
+
+    // Set extra headers if configured
+    if (store.headers_json) {
+      try {
+        const headers = JSON.parse(store.headers_json);
+        await page.setExtraHTTPHeaders(headers);
+      } catch { /* ignore invalid headers */ }
+    }
+
+    // Navigate to the page
+    const response = await page.goto(searchUrl, {
+      waitUntil: 'networkidle2',
+      timeout: NAVIGATION_TIMEOUT,
+    });
+
+    const statusCode = response?.status() ?? 200;
+
+    // Wait for the product container to appear
+    try {
+      await page.waitForSelector(store.sel_container, { timeout: PAGE_TIMEOUT });
+    } catch {
+      // Container might not exist if no results — return empty
+      const html = await page.content();
+      return { items: [], html, statusCode };
+    }
+
+    // Small extra wait for any remaining renders
+    await new Promise((r) => setTimeout(r, 500));
+
+    // Extract product data from the rendered DOM
+    const items = await page.evaluate((selectors) => {
+      const containers = document.querySelectorAll(selectors.container);
+      const results: Array<{ name: string; priceText: string; link: string; image: string | null }> = [];
+
+      containers.forEach((el) => {
+        const nameEl = el.querySelector(selectors.name);
+        const priceEl = el.querySelector(selectors.price);
+        const linkEl = el.querySelector(selectors.link) as HTMLAnchorElement | null;
+        const imageEl = selectors.image ? el.querySelector(selectors.image) as HTMLImageElement | null : null;
+
+        const name = nameEl?.textContent?.trim() || '';
+        const priceText = priceEl?.textContent?.trim() || '';
+        const link = linkEl?.getAttribute('href') || '';
+        const image = imageEl?.getAttribute('src') || imageEl?.getAttribute('data-src') || null;
+
+        if (name && priceText) {
+          results.push({ name, priceText, link, image });
+        }
+      });
+
+      return results;
+    }, {
+      container: store.sel_container,
+      name: store.sel_name,
+      price: store.sel_price,
+      link: store.sel_link,
+      image: store.sel_image || null,
+    });
+
+    const html = await page.content();
+
+    return { items, html, statusCode };
+  } finally {
+    await page.close();
+  }
+}
+
+export async function closeBrowser(): Promise<void> {
+  if (browser) {
+    await browser.close();
+    browser = null;
+  }
+}