feat: install the Quest build from the website

A Quest page on the public site (/quest) installs a DorkNet .xapk from
Chrome or Edge over WebUSB, with no adb, SideQuest or scripts: pick the
.xapk, connect the headset, install. It installs the APK, copies the OBB
to its install path (skipped when an identical one is already there) and
launches the app, with progress bars and plain-language errors for an
unsupported browser, a headset held by adb/SideQuest, a disconnect and a
copy signed with a different key.

The .xapk is read from the player's own disk: the APK and OBB are stored
uncompressed, so they stream straight out of the file without loading
1.4 GB into memory, and the server never hosts game files.

Uses Tango (@yume-chan/adb 2.6.4 and friends, MIT), pinned and bundled;
the page is lazy-loaded so the rest of the site doesn't grow. Credited in
NOTICE; README, DorkNet.Quest/README.md, docs/quest.md and the packaged
README.txt point players at the page.

DorkNet.Quest/README.md

@@ -129,7 +129,18 @@ the running `libil2cpp.so`, so a table can never be applied to the wrong build.
 
 ## Install
 
-From a release folder, one command does everything (finds adb and the headset,
+**From the browser (easiest).** Open the **Quest** page of your DorkNet site
+(`https://<apex>/quest`) in Chrome or Edge on a computer, plug the headset in
+over USB, pick the `.xapk`, click **Connect**, accept "Allow USB debugging" in
+the headset, then **Install**. The page talks to the headset over WebUSB
+(Tango, `@yume-chan/adb`): it installs the APK, copies the OBB to its install
+path (skipped if an identical one is already there) and launches the app. The
+`.xapk` never leaves the player's computer; the server hosts no game files.
+Close SideQuest / Meta Quest Developer Hub, or run `adb kill-server`, first:
+only one program can hold the headset's USB connection. Firefox, Safari and
+phones don't support WebUSB.
+
+**From a release folder**, one command does everything (finds adb and the headset,
 installs the APK, copies the OBB to the right path, skips the OBB if it is
 already there, and launches the app):
 

DorkNet.Quest/scripts/package.ps1

@@ -150,7 +150,9 @@ $($manifest.name) $verName - Rec Room for DorkNet (Meta Quest)
 
 1. Turn on developer mode for your headset (Meta Horizon phone app), plug it
    in over USB and accept "Allow USB debugging" inside the headset.
-2. Install:
+2. Install. Easiest: open the Quest page of your DorkNet server's website
+   (https://<server>/quest) in Chrome or Edge, pick this .xapk and follow the
+   steps. Or use the scripts here:
      Windows:        double-click install.cmd
      macOS / Linux:  ./install.sh
    The installer needs adb (Android platform-tools) on PATH or in