Add EHSAN favicon and localized browser tab titles (Task #21)

The browser tab previously showed a generic placeholder favicon and the
English title "EHSAN Closed Donation Loop". Per the reference, the tab now
shows the EHSAN logo mark and an Arabic platform title.

Changes:
- Favicon: copied the existing EHSAN logo (src/assets/ehsan-logo.png) to
  public/favicon.png and pointed index.html at %BASE_URL%favicon.png
  (base-path safe; verified it serves 200 image/png).
- Static head: index.html <title> and OG/Twitter titles + description now
  use the Arabic platform name "منصة إحسان".
- Per-page titles: added a DocumentTitle component
  (src/hooks/useDocumentTitle.ts) rendered in the Router that sets
  document.title to "<page name> - <platform>" based on the current wouter
  path and active language, reading from a new translations.meta section
  (AR + EN). Home reads "الصفحة الرئيسية - منصة إحسان"; switches with language.

Approach note: titles are centralized in the router rather than edited into
each page file, keeping it DRY while covering all main routes.

Verified: tsc clean; e2e confirmed titles on /, /opportunities, /cart and
English fallback ("Home - EHSAN Platform"), plus favicon load.

artifacts/ehsan-poc/src/hooks/useDocumentTitle.ts

@@ -0,0 +1,33 @@
+import { useEffect } from "react";
+import { useLocation } from "wouter";
+import { useLanguage } from "../contexts/LanguageContext";
+
+function pageNameForPath(path: string, meta: Record<string, string>): string {
+  if (path === "/" || path === "") return meta.home;
+  if (path.startsWith("/opportunities")) return meta.opportunities;
+  if (path.startsWith("/cart")) return meta.cart;
+  if (path.startsWith("/about")) return meta.about;
+  if (path.startsWith("/track")) return meta.track;
+  if (path.startsWith("/donate")) return meta.donate;
+  if (path.startsWith("/request")) return meta.request;
+  if (path.startsWith("/waqf")) return meta.waqf;
+  if (path.startsWith("/baraem")) return meta.baraem;
+  if (path.startsWith("/admin")) return meta.admin;
+  if (path.startsWith("/whatsapp-log")) return meta.whatsappLog;
+  if (path.startsWith("/thank-you")) return meta.thankYou;
+  if (path.startsWith("/login")) return meta.login;
+  return "";
+}
+
+export function DocumentTitle() {
+  const [location] = useLocation();
+  const { t } = useLanguage();
+
+  useEffect(() => {
+    const meta = t.meta as Record<string, string>;
+    const name = pageNameForPath(location, meta);
+    document.title = name ? `${name} - ${meta.platform}` : meta.platform;
+  }, [location, t]);
+
+  return null;
+}