feat(site): Downloads page and Quest install from the latest build

When the server is pointed at the bucket CI publishes builds to
(DorkNet:Downloads:BaseUrl), the site lists them on a new Downloads page and
the Quest page offers "Latest build" next to "Choose file".

The server reads manifest.json and the files over HTTP on the internal network
and streams them through with Range support (DownloadsController); only files
the manifest lists are served. The xapk reader now reads from a byte source,
either the picked File or the server URL via Range requests, so the browser
installer streams the APK and OBB to the headset without downloading the
package first. Unset, both features stay hidden.

DorkNet.Server/site/src/pages/Quest.tsx

@@ -1,6 +1,8 @@
-import { useRef, useState } from 'react';
-import { openXapk, type Xapk } from '../lib/xapk';
+import { useEffect, useRef, useState } from 'react';
+import { useSearchParams } from 'react-router';
+import { fileSource, openXapk, urlSource, type Xapk } from '../lib/xapk';
 import { connectHeadset, installXapk, webUsbSupported, type Headset, type Progress } from '../lib/questInstall';
+import { fileUrl, getDownloads, latestQuest } from '../lib/downloads';
 
 const fmtSize = (n: number) =>
   n >= 1e9 ? `${(n / 1e9).toFixed(2)} GB` : n >= 1e6 ? `${(n / 1e6).toFixed(1)} MB` : `${Math.max(1, Math.round(n / 1e3))} KB`;
@@ -43,15 +45,35 @@ export function Quest() {
   const [err, setErr] = useState<string | null>(null);
   const [done, setDone] = useState(false);
   const fileRef = useRef<HTMLInputElement>(null);
+  // The server's latest published Quest build, if it offers downloads.
+  const [latest, setLatest] = useState<ReturnType<typeof latestQuest>>(null);
+  const [params] = useSearchParams();
 
-  const pickFile = async (f: File | undefined) => {
-    if (!f) return;
+  const open = async (load: () => Promise<Xapk>) => {
     setErr(null); setDone(false); setProgress({}); setBusy('file');
-    try { setXapk(await openXapk(f)); }
+    try { setXapk(await load()); }
     catch (e) { setXapk(null); setErr((e as Error).message); }
     finally { setBusy(null); }
   };
 
+  const pickFile = async (f: File | undefined) => {
+    if (f) await open(() => openXapk(fileSource(f)));
+  };
+
+  const pickLatest = async (l = latest) => {
+    if (l) await open(() => openXapk(urlSource(fileUrl(l.file), l.file.name, l.file.size)));
+  };
+
+  useEffect(() => {
+    getDownloads().then((m) => {
+      const l = latestQuest(m);
+      setLatest(l);
+      // Arriving from the Downloads page's "Install on Quest".
+      if (l && params.get('build') === 'latest') void pickLatest(l);
+    }).catch(() => { /* no downloads: only the file picker */ });
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
   const connect = async () => {
     setErr(null); setBusy('connect');
     try { setHeadset(await connectHeadset()); }
@@ -108,19 +130,32 @@ export function Quest() {
         </div>
       )}
 
-      <Step n={1} title="Choose the .xapk file" done={!!xapk}>
-        <p className="text-sm text-ink-400">Pick the <code className="text-ink-200">DorkNet-….xapk</code> you were given. It stays on your computer; nothing is uploaded.</p>
+      <Step n={1} title={latest ? 'Pick the build' : 'Choose the .xapk file'} done={!!xapk}>
+        {latest ? (
+          <p className="text-sm text-ink-400">
+            Install the latest build straight from this server: nothing to download first, it streams to the
+            headset during the install. Or pick a <code className="text-ink-200">.xapk</code> you already have.
+          </p>
+        ) : (
+          <p className="text-sm text-ink-400">Pick the <code className="text-ink-200">DorkNet-….xapk</code> you were given. It stays on your computer; nothing is uploaded.</p>
+        )}
         <input ref={fileRef} type="file" accept=".xapk,.zip" className="hidden" onChange={(e) => pickFile(e.target.files?.[0])} />
         <div className="flex flex-wrap items-center gap-3">
-          <button className="btn-secondary" disabled={busy !== null} onClick={() => fileRef.current?.click()}>
-            {busy === 'file' ? 'Reading…' : xapk ? 'Choose a different file' : 'Choose file'}
-          </button>
-          {xapk && (
-            <span className="text-sm text-ink-300">
-              <span className="text-ink-100 font-medium">{name}</span> {xapk.manifest.version_name} · {fmtSize(totalSize)}
-            </span>
+          {latest && (
+            <button className="btn-primary" disabled={busy !== null} onClick={() => pickLatest()}>
+              {busy === 'file' ? 'Reading…' : `Latest build: ${latest.release.title}${latest.file.build ? ` (build ${latest.file.build})` : ''}`}
+            </button>
           )}
+          <button className="btn-secondary" disabled={busy !== null} onClick={() => fileRef.current?.click()}>
+            {busy === 'file' && !latest ? 'Reading…' : xapk && !latest ? 'Choose a different file' : 'Choose file'}
+          </button>
         </div>
+        {xapk && (
+          <p className="text-sm text-ink-300">
+            Selected: <span className="text-ink-100 font-medium">{name}</span> {xapk.manifest.version_name} · {fmtSize(totalSize)}
+            <span className="text-ink-500"> · {xapk.source.name}</span>
+          </p>
+        )}
       </Step>
 
       <Step n={2} title="Connect your headset" done={!!headset}>