fix(pwa): the installed app can rotate, and "New Message" opens a new DM (#292)

manifest.json locked the installed app to portrait (no landscape video,
screenshare or call view on Android / tablets) and its "New Message"
shortcut pointed at /, the home page. Drop the orientation lock and
point the shortcut at ./direct/create/ (Create Chat).

Fixes #292

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

public/manifest.json

@@ -5,7 +5,6 @@
   "dir": "auto",
   "lang": "en-US",
   "display": "standalone",
-  "orientation": "portrait",
   "start_url": "./",
   "background_color": "#0a0a0a",
   "theme_color": "#980000",
@@ -90,7 +89,7 @@
       "name": "New Message",
       "short_name": "DM",
       "description": "Open a new direct message",
-      "url": "/",
+      "url": "./direct/create/",
       "icons": [
         {
           "src": "public/res/android/android-chrome-96x96.png",