chore: rename project from podpuddle to podsteadr

Renames the repo directory and every podpuddle/PODPUDDLE reference
across code, config, and docs to podsteadr/PODSTEADR (package names,
Docker Compose project/service/volume names, env var names, UI/RSS
strings). Existing Docker volume data (uploaded blobs, mediamtx
recordings, the server's sqlite DB and its nostr identity key) was
migrated to new podsteadr_-prefixed volumes with matching filenames
so it isn't orphaned by the rename.

mediamtx/mediamtx.yml

@@ -1,6 +1,6 @@
-# MediaMTX configuration for podpuddle.
+# MediaMTX configuration for podsteadr.
 # Ingest: RTMP (OBS) + WebRTC/WHIP (browser). Output: HLS. Publish auth is
-# delegated to podpuddle via HTTP; stream status is polled from the API.
+# delegated to podsteadr via HTTP; stream status is polled from the API.
 
 logLevel: info
 
@@ -9,7 +9,7 @@ apiAddress: :9997
 
 # ---- authentication ------------------------------------------------------
 authMethod: http
-authHTTPAddress: http://podpuddle:8095/api/mediamtx/auth
+authHTTPAddress: http://podsteadr:8095/api/mediamtx/auth
 authHTTPExclude:
   - action: api
   - action: metrics
@@ -45,5 +45,5 @@ pathDefaults:
 
 paths:
   # Streams live at live/<streamId>; publish requires the stream secret,
-  # which podpuddle checks in the auth webhook.
+  # which podsteadr checks in the auth webhook.
   "~^live/[A-Za-z0-9]+$": {}