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>

docker-compose.yml

@@ -1,7 +1,7 @@
 services:
-  ipodderx:
-    image: 192.168.1.130:5000/ipodderx:latest
-    container_name: iPodderX
+  ipx:
+    image: 192.168.1.130:5000/ipx:latest
+    container_name: iPX
     restart: unless-stopped
     environment:
       PUID: "99"
@@ -10,15 +10,15 @@ services:
       IPX_LOG: "ipx=info"
     # IPX_DATABASE_URL=postgres://... to use Postgres; without it, /data/state.db (SQLite).
     env_file:
-      - ipodderx.env   # relative: Arcane resolves it inside its own container
+      - ipx.env   # relative: Arcane resolves it inside its own container
     ports:
       - "8099:8099"          # web UI
       - "6881:6881/tcp"      # BitTorrent peers
       - "6881:6881/udp"      # DHT
     volumes:
-      - /mnt/fast/appdata/ipodderx:/config     # config.toml, and the web token
-      - /mnt/user/ipodderx/:/data         # state.db
-      - /mnt/user/ipodderx/downloads:/downloads
+      - /mnt/fast/appdata/ipx:/config     # config.toml, and the web token
+      - /mnt/user/ipx/:/data         # state.db
+      - /mnt/user/ipx/downloads:/downloads
     healthcheck:
       test: ["CMD", "ipx", "status"]
       interval: 30s