Rename iPodderX to iPX (#56)

The app, the repository (rays/ipx), the image, the compose service and
container, and the data folders on Tower take the new name. What stays:
the 2004 iPodderX and ipodderx-core, which are history; the Postgres
database and login, and ipodderx.sdf1.net with its Access and Authentik
apps, which would each need moving outside this repo; and the first-start
password, as ipx is shorter than the eight characters a password needs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/index.html

@@ -4,7 +4,7 @@
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover">
 <meta name="color-scheme" content="dark light">
-<title>iPodderX</title>
+<title>iPX</title>
 <link rel="icon" type="image/png" sizes="128x128" href="/favicon.png">
 <link rel="apple-touch-icon" href="/apple-touch-icon.png">
 <link rel="stylesheet" data-src="app.css">
@@ -34,7 +34,7 @@
 <div id="shell">
   <aside id="sidebar">
     <div class="brand">
-      <img class="logo" src="/logo.svg" alt="iPodderX"><h1>iPodderX</h1>
+      <img class="logo" src="/logo.svg" alt="iPX"><h1>iPX</h1>
     </div>
     <div class="searchwrap"><input type="search" id="feedFilter" placeholder="Filter feeds…"></div>
     <div id="feedlist"></div>